USMLE Step 1 reproductive system questions

SRY (sex-determining region Y) encodes a transcription factor that upregulates SOX9, driving differentiation of supporting cells in the gonadal ridge into Sertoli cells. Sertoli cells then secrete anti-Mullerian hormone (Mullerian inhibitory factor), which causes regression of the paramesonephric (Mullerian) ducts. Leydig cells differentiate later and produce testosterone, but SRY's direct target lineage is the Sertoli cell. Granulosa and theca cells are ovarian derivatives that form in the absence of SRY expression.

• B. Germ cells are not directed by SRY to differentiate; they migrate into the gonadal ridge from the yolk sac independently of sex determination.
• C. Granulosa cells are the ovarian analog of Sertoli cells and arise when SRY is absent.
• D. Leydig cells produce testosterone but differentiate secondary to Sertoli cell signaling, not as the direct SRY target.
• E. Theca cells are ovarian stromal derivatives that arise in the absence of SRY, analogous to Leydig cells.

In androgen insensitivity syndrome, the androgen receptor is nonfunctional, so target tissues fail to respond to testosterone and dihydrotestosterone, producing a female external phenotype with testes, but Sertoli cell function is intact and anti-Mullerian hormone (Mullerian inhibitory factor) is produced normally and signals through its own receptor. This causes normal regression of the Mullerian ducts, explaining the absent uterus and vagina ending blindly, despite a 46,XY karyotype and normal to elevated testosterone. Breast development occurs because unopposed testosterone is peripherally aromatized to estrogen.

• A. 21-hydroxylase deficiency causes virilization in 46,XX females, not a 46,XY phenotypic female with absent uterus.
• B. SRY failure would result in a streak gonad and persistence of Mullerian structures, which contradicts the absent uterus.
• D. The androgen receptor mutation explains the external phenotype and pubic hair pattern, but the uterine absence specifically results from normal AMH action, not from the receptor defect itself.
• E. 5-alpha-reductase deficiency causes ambiguous genitalia with a normal uterus absent because AMH is still produced, but it does not explain breast development or female-typical presentation at puberty as well as androgen receptor defect.

5-alpha-reductase type 2 deficiency impairs conversion of testosterone to dihydrotestosterone (DHT) in the external genitalia, which normally requires DHT for formation of the penis, scrotum, and prostate in utero, resulting in ambiguous or female-appearing genitalia at birth despite normal testicular testosterone production. At puberty, the large testosterone surge is high enough to activate androgen receptors directly, even with minimal DHT, driving phallic growth, voice change, and muscle mass increase ('penis at twelve' phenomenon). Anti-Mullerian hormone acted earlier in gestation and is unrelated to this pubertal virilization. The enzyme defect itself does not resolve; it is simply overcome by the markedly higher testosterone concentration.

• B. The enzyme defect is a fixed genetic mutation and does not correct itself at puberty.
• C. Adrenal androgens are not the primary driver; this is a gonadal testosterone effect overcoming the enzymatic block.
• D. Increased aromatization to estrogen would promote feminization, not virilization.
• E. AMH acts prenatally to regress Mullerian ducts and has no role in pubertal virilization.

Classic salt-wasting congenital adrenal hyperplasia results from 21-hydroxylase deficiency, which blocks conversion of progesterone and 17-hydroxyprogesterone to the mineralocorticoid and glucocorticoid pathways, causing low aldosterone and low cortisol with marked buildup of 17-hydroxyprogesterone. Low aldosterone produces hyponatremia, hyperkalemia, and hypovolemia, while low cortisol contributes to hypoglycemia and loss of negative feedback, raising ACTH, which drives excess shunting of precursors into androgen synthesis causing virilization of the external genitalia in a 46,XX fetus. The internal genitalia (uterus, ovaries) remain female because the fetal ovaries do not produce anti-Mullerian hormone.

• A. Aldosterone is low, not elevated, in classic 21-hydroxylase deficiency, which is why salt-wasting occurs.
• B. 17-hydroxyprogesterone is elevated, not low, because the enzyme block causes its accumulation.
• C. Adrenal androgens are elevated, not low, accounting for the virilized genitalia seen in this infant.
• D. Cortisol is low in 21-hydroxylase deficiency, and the electrolyte derangements described are inconsistent with normal electrolytes.

The uterus, cervix, and upper vagina form from fusion of the caudal portions of the paired paramesonephric (Mullerian) ducts; when this fusion fails completely, two separate uterine horns, two cervices, and often a longitudinal vaginal septum result, producing uterus didelphys. Agenesis of both ducts would cause absence of the uterus and vagina (as in Mayer-Rokitansky-Kuster-Hauser syndrome), not duplication. Persistent mesonephric (Wolffian) duct remnants, such as Gartner duct cysts, are unrelated to Mullerian fusion defects. Incomplete resorption of the septum after the ducts have fused produces a septate uterus, which has a single external uterine contour rather than two separate horns and cervices.

• B. Incomplete septal resorption after fusion produces a septate uterus with one external contour, not two separate cervices as described.
• C. Persistent mesonephric ducts give rise to structures like Gartner duct cysts, not duplicated Mullerian derivatives.
• D. Urogenital sinus abnormalities affect the lower vagina and bladder, not the fusion of the uterine horns.
• E. Agenesis of both ducts would cause absence of the uterus and vagina, not duplicated structures.

Epispadias results from abnormal positioning of the genital tubercle during development, which leads to a ventral (anterior) location of the urethral folds relative to normal; this same mispositioning disrupts normal closure of the infraumbilical abdominal wall and is strongly associated with bladder exstrophy, as seen in infant B. Hypospadias, in contrast, results from incomplete closure of the urethral folds on the ventral penile surface, producing a ventral meatus, and is not typically associated with exstrophy. The processus vaginalis relates to testicular descent and inguinal hernias, not urethral position. Persistent Mullerian structures in a male arise from anti-Mullerian hormone deficiency or receptor defects, unrelated to urethral meatus position.

• A. This description matches the mechanism of hypospadias (infant A), not epispadias.
• C. Mullerian duct persistence is unrelated to the external genital defect described.
• D. This describes a mechanism unrelated to the genital tubercle mispositioning that causes epispadias and exstrophy.
• E. Processus vaginalis persistence causes communicating hydrocele or hernia, not abnormal urethral meatus position.

Ovulation occurs approximately 24-36 hours after the LH surge, and the rise in basal body temperature is caused by the thermogenic effect of progesterone secreted by the newly formed corpus luteum after ovulation. Because progesterone secretion begins only after the follicle ruptures, the BBT rise lags behind ovulation by about 1-2 days. Therefore, if the sustained temperature rise begins on day 16, ovulation most likely occurred around day 14. This relationship is used clinically to retrospectively estimate the fertile window, though BBT cannot predict ovulation prospectively since the rise occurs after the fact.

• A. Ovulation occurs before, not after, the BBT rise, since progesterone secretion (which raises BBT) follows ovulation.
• B. This delay is too long and reverses the correct temporal sequence of ovulation preceding the BBT rise.
• D. Ovulation precedes the progesterone-driven BBT rise; it does not occur simultaneously with it.
• E. This would place ovulation before the temperature rise by too great a margin, inconsistent with the typical 1-2 day lag.

In early pregnancy, the corpus luteum (maintained by hCG) produces progesterone and estrogen, but by 8-10 weeks the placenta takes over as the dominant source of estrogen, a transition called the luteal-placental shift. The placenta lacks 17α-hydroxylase/17,20-lyase activity and cannot synthesize androgens de novo, so it depends on the fetal adrenal gland to produce dehydroepiandrosterone sulfate (DHEA-S), which the placental syncytiotrophoblast then aromatizes into estrogens, especially estriol. This fetoplacental unit explains why estriol levels reflect fetal well-being. Low maternal estriol can indicate fetal adrenal insufficiency or placental dysfunction.

• A. The maternal adrenal cortex is not the primary source of pregnancy estrogen; it lacks the fetal-placental cooperation required for estriol synthesis.
• C. The fetal liver contributes to steroid metabolism but does not synthesize estrogen directly; it lacks aromatase activity for this pathway.
• D. The maternal ovarian stroma does not become the estrogen source in later pregnancy; ovarian function is largely quiescent once the placenta takes over.
• E. The corpus luteum regresses in function after the first trimester as the placenta takes over estrogen and progesterone production.

Human chorionic gonadotropin (hCG), secreted by the syncytiotrophoblast beginning around the time of implantation, shares an identical alpha subunit with LH, FSH, and TSH, and has a beta subunit structurally similar to LH. Because of this homology, hCG binds the LH/hCG receptor on corpus luteum cells, mimicking the LH surge and rescuing the corpus luteum from regression (preventing luteolysis). This sustains progesterone secretion that maintains the endometrium until the placenta takes over steroidogenesis. hCG's unique beta subunit and longer half-life (due to extensive glycosylation) allow it to be detected in urine and serve as the basis for pregnancy testing.

• A. The corpus luteum requires continued trophic support; without hCG rescue, it undergoes luteolysis and progesterone falls, leading to menstruation.
• C. FSH receptors are not the primary mechanism maintaining the corpus luteum in pregnancy; hCG acting on LH receptors is key.
• D. Estrogen does not directly rescue the corpus luteum; the rescue signal is the glycoprotein hormone hCG acting via LH receptors.
• E. Progesterone synthesis in the corpus luteum remains LH/hCG receptor-dependent, not ACTH-dependent.

Menopause results from age-related depletion of ovarian follicles, which leads to decreased production of estrogen and inhibin B by granulosa cells. Because estrogen and inhibin normally exert negative feedback on the hypothalamus and anterior pituitary, their decline removes this inhibition, causing a compensatory rise in GnRH pulsatility and pituitary FSH and LH secretion. FSH rises earlier and to a greater degree than LH because inhibin B selectively suppresses FSH. This pattern of low estrogen with markedly elevated FSH and LH is the biochemical hallmark of menopause.

• A. A gonadotropin-secreting pituitary adenoma is rare and would not explain the concurrent low estradiol from ovarian failure.
• B. Hypothalamic hypersensitivity to estrogen is not the mechanism; the problem is loss of estrogen and inhibin production from depleted follicles.
• C. Increased peripheral aromatization would raise estrogen, not lower it, and does not explain the elevated gonadotropins seen here.
• D. Autoimmune gonadotroph destruction would cause low, not elevated, gonadotropins.

Oxytocin, synthesized in the hypothalamus and released from the posterior pituitary, acts on a Gq-coupled oxytocin receptor present on uterine myometrial smooth muscle cells and on myoepithelial cells surrounding mammary alveoli. Receptor activation stimulates phospholipase C, generating IP3 and diacylglycerol, which raises intracellular calcium and triggers smooth muscle contraction. In the myometrium this produces coordinated uterine contractions during labor, and in the breast it causes myoepithelial cell contraction leading to milk ejection (letdown). Sensory or even psychogenic stimuli, such as hearing an infant cry, can trigger oxytocin release via neuroendocrine reflex arcs, explaining anticipatory letdown.

• B. Gs-coupled cAMP signaling is not the oxytocin receptor pathway; oxytocin uses Gq-PLC-IP3 signaling.
• C. Oxytocin acts through a Gq-coupled GPCR, not a receptor tyrosine kinase or JAK-STAT signaling.
• D. Oxytocin requires its membrane receptor to initiate signaling; it does not act directly on calcium channels.
• E. Oxytocin is a peptide hormone acting on a cell-surface receptor, not a steroid acting on nuclear receptors.

Sertoli cells secrete inhibin B, a glycoprotein hormone that selectively suppresses FSH secretion from the anterior pituitary gonadotrophs through negative feedback, largely independent of the testosterone-LH feedback loop. When Sertoli cell number or function is reduced, as in this patient's biopsy findings, inhibin B levels fall, removing this feedback and causing FSH to rise. Because Leydig cells are preserved and continue producing testosterone, the testosterone-LH feedback loop remains intact, explaining the normal LH and testosterone levels. This dissociation between elevated FSH and normal LH/testosterone is a classic pattern of isolated Sertoli cell dysfunction (as seen in some cases of germ cell aplasia or chemotherapy/radiation damage).

• A. Testosterone is produced by Leydig cells, not Sertoli cells, and primarily feeds back to suppress LH, not FSH.
• B. Androgen-binding protein acts locally within the seminiferous tubules to concentrate testosterone; it does not directly stimulate pituitary gonadotrophs.
• D. Leydig cells are preserved, not hyperplastic, and testosterone does not selectively stimulate FSH; it feeds back mainly on LH.
• E. GnRH pulse frequency changes affect the ratio of LH to FSH release, but this does not explain selective FSH elevation from Sertoli cell loss; inhibin B loss is the specific mechanism.

LH acts on Leydig cells through a Gs-coupled LH receptor, activating adenylate cyclase to increase intracellular cAMP and activate protein kinase A. This signaling cascade upregulates steroidogenic acute regulatory protein (StAR), which transports cholesterol into the mitochondria, and increases activity of cholesterol side-chain cleavage enzyme (CYP11A1, desmolase), the rate-limiting step converting cholesterol to pregnenolone. This initiates the steroidogenic pathway leading to testosterone production in Leydig cells. This cAMP-PKA mechanism is analogous to ACTH's action on adrenal steroidogenesis, reflecting shared signaling logic across steroid-producing endocrine cells.

• B. LH acts through a cell-surface G protein-coupled receptor, not an intracellular nuclear receptor, and does not primarily regulate aromatase in Leydig cells.
• C. LH receptor signaling is G protein-coupled, not a receptor tyrosine kinase, and its key action is not on 5-alpha reductase.
• D. LH does not transport cholesterol directly; it signals through cAMP to upregulate StAR protein, which mediates mitochondrial cholesterol transport.
• E. LH receptor signaling in Leydig cells is Gs-coupled (cAMP-dependent), not Gq-coupled, and its primary target is the rate-limiting desmolase step, not 17-beta hydroxysteroid dehydrogenase.

Exogenous anabolic steroids raise circulating androgen levels, which negatively feed back on the hypothalamic-pituitary axis, suppressing GnRH pulsatility and thus LH and FSH secretion. Reduced LH decreases endogenous testicular testosterone production by Leydig cells, and reduced FSH decreases Sertoli cell support of spermatogenesis, causing testicular atrophy and infertility despite high serum testosterone (from the exogenous source). This is the same mechanism underlying exogenous testosterone's contraceptive effect in men. Stopping the drug allows gradual recovery of the HPG axis in most cases.

• A. Leydig cells are not directly destroyed; they become atrophic due to lack of LH stimulation, not direct toxicity.
• B. There is no autoimmune mechanism involved in steroid-induced testicular atrophy.
• C. Anabolic steroids act as agonists, not competitive antagonists, at androgen receptors.
• D. Aromatization to estradiol contributes to gynecomastia but is not the primary mechanism of testicular atrophy.

Klinefelter syndrome (47,XXY) results from an extra X chromosome, causing dysgenesis of the seminiferous tubules. The hallmark histologic finding is hyalinization and fibrosis of the seminiferous tubules, often with apparent clustering of Leydig cells due to the loss of surrounding tubular tissue (though total Leydig cell function is impaired). This leads to low testosterone with compensatory elevation of LH and FSH (hypergonadotropic hypogonadism), along with small firm testes, gynecomastia, and infertility due to azoospermia.

• A. Granulomatous inflammation is seen in infectious orchitis, not in Klinefelter syndrome.
• B. Maturation arrest implies a focal defect in spermatogenesis, not the diffuse tubular dysgenesis seen in Klinefelter syndrome.
• C. Leydig cells are present, though their number may appear relatively increased due to tubular loss, not absent.
• D. Seminiferous tubules are hyalinized and fibrotic, not replaced by adipose tissue.

Finasteride inhibits type 2 5-alpha-reductase, the enzyme that converts testosterone to dihydrotestosterone (DHT) in peripheral tissues such as the prostate and skin. DHT is a more potent androgen than testosterone and is the main driver of prostatic growth and hyperplasia in BPH, as well as androgenic hair growth and male pattern baldness. Because serum testosterone levels remain largely unchanged, the clinical effects (decreased prostate size, reduced body hair, improved scalp hair) are explained by reduced DHT rather than reduced testosterone. This distinguishes finasteride from alpha-1 blockers, which relieve symptoms without affecting prostate size.

• A. Alpha-1 blockers (e.g., tamsulosin) relieve symptoms by relaxing smooth muscle but do not shrink the prostate or affect hair growth.
• B. Aromatase inhibitors reduce estradiol and are not the mechanism used in standard BPH treatment.
• D. There is no suppression of LH or change in testosterone with 5-alpha-reductase inhibitors.
• E. Androgen receptor blockade (e.g., by flutamide) would not explain the unchanged testosterone and selective DHT-related effects described.

In PCOS, peripheral insulin resistance leads to compensatory hyperinsulinemia. Insulin acts synergistically with LH on ovarian theca cells, stimulating excess androgen (testosterone and androstenedione) production. Hyperinsulinemia also decreases hepatic synthesis of sex hormone-binding globulin (SHBG), raising free testosterone further. The elevated LH:FSH ratio (classically greater than 2:1 or 3:1) reflects increased GnRH pulse frequency, which favors LH synthesis over FSH, contributing to anovulation and the hyperandrogenic state.

• A. Hyperinsulinemia does not primarily act by increasing peripheral aromatization in PCOS pathophysiology.
• B. Insulin does not decrease GnRH receptor sensitivity; the LH:FSH ratio is elevated, not decreased, due to increased GnRH pulse frequency.
• C. FSH is produced by the pituitary, not the liver, and insulin does not directly suppress it this way.
• E. PCOS androgen excess is ovarian (theca cell) in origin, not due to primary adrenal hyperplasia.

Asherman syndrome results from intrauterine adhesions (synechiae) that form after aggressive endometrial curettage, particularly when performed on a gravid or postpartum uterus, which damages the basal layer of the endometrium and impairs its regenerative capacity. This produces secondary amenorrhea with normal gonadotropin and prolactin levels, since the hypothalamic-pituitary-ovarian axis is intact; the defect is at the level of the endometrium itself. A negative response to progestin challenge, combined with normal hormone levels, points to an anatomic uterine cause rather than an endocrine one; hysteroscopy showing intrauterine adhesions confirms the diagnosis.

• A. Hyperprolactinemia would be reflected by an elevated prolactin level, which is normal in this patient.
• C. Hypothalamic suppression typically presents with low LH/FSH and estrogen deficiency, not normal gonadotropins with a history of uterine instrumentation.
• D. Premature ovarian insufficiency would present with elevated FSH and LH and symptoms of estrogen deficiency, not seen here.
• E. Cervical stenosis typically follows cervical procedures (e.g., cone biopsy) rather than uterine curettage, and would not fully explain absent withdrawal bleeding in this clinical context.

Primary ovarian insufficiency (formerly premature ovarian failure) is diagnosed in women under age 40 with amenorrhea for at least 4 months and two serum FSH levels in the menopausal range (typically greater than 25-40 mIU/mL) measured at least one month apart, accompanied by low estradiol. The elevated FSH reflects loss of negative feedback from the ovary due to follicular depletion or dysfunction, and symptoms of estrogen deficiency such as hot flashes are common. Causes include autoimmune oophoritis, chromosomal abnormalities (e.g., Fragile X premutation, Turner mosaicism), and prior chemotherapy or radiation.

• A. Hypothalamic amenorrhea causes low or normal FSH and low estradiol due to decreased GnRH drive, not elevated FSH.
• B. Asherman syndrome is an anatomic uterine cause of amenorrhea with normal FSH and estradiol levels, not hormonally abnormal.
• C. PCOS presents with a normal or low FSH, elevated LH:FSH ratio, and signs of hyperandrogenism, not elevated FSH with low estradiol.
• D. A prolactinoma would present with elevated prolactin and typically low or normal FSH, not an elevated FSH consistent with ovarian failure.

Clomiphene citrate is a selective estrogen receptor modulator that acts as a competitive antagonist at hypothalamic estrogen receptors. By blocking estrogen's negative feedback at the hypothalamus, it increases GnRH pulsatility, which in turn increases pituitary LH and FSH secretion. This rise in gonadotropins stimulates ovarian follicular development and ovulation, making clomiphene a first-line agent for ovulation induction in anovulatory infertility such as PCOS.

• A. Clomiphene acts on estrogen receptors, not GnRH receptors, and it is an antagonist, not an agonist, at its target receptor.
• B. Clomiphene does not inhibit aromatase; that mechanism describes letrozole, a different ovulation induction agent.
• D. Clomiphene does not bind FSH receptors directly; its effect is mediated indirectly through increased endogenous gonadotropin secretion.
• E. Clomiphene does not act on kisspeptin neurons; its primary target is hypothalamic estrogen receptors.

A varicocele is an abnormal dilation of the pampiniform venous plexus, most commonly on the left side due to the left testicular vein draining at a right angle into the left renal vein, predisposing to venous stasis and reflux. This dilation impairs the normal countercurrent heat exchange mechanism that keeps testicular temperature below core body temperature, leading to increased intratesticular temperature. Elevated temperature impairs spermatogenesis, resulting in decreased sperm count, motility, and abnormal morphology, making varicocele the most common correctable cause of male infertility.

• A. Varicocele does not cause mechanical obstruction of the epididymis; sperm transport is not primarily affected.
• B. There is no mechanism of retrograde adrenal metabolite toxicity in varicocele; this is not an established pathway.
• D. Varicocele involves venous pooling and increased pressure, not reduced arterial inflow or ischemia.
• E. Varicocele does not directly disrupt the blood-testis barrier to cause autoimmune sperm destruction.

Choriocarcinoma is a malignant gestational trophoblastic neoplasm composed of anaplastic cytotrophoblasts and syncytiotrophoblasts without chorionic villi. It commonly follows a molar pregnancy (about 50% of cases), normal pregnancy, or abortion, and is characterized by markedly elevated beta-hCG and early hematogenous spread, most often to the lungs, producing the classic 'cannonball' metastatic nodules seen on chest imaging. The absence of villi distinguishes it from a hydatidiform mole. It is highly chemosensitive and is treated with methotrexate-based regimens.

• A. The biopsy shows trophoblastic tissue, not glandular carcinoma cells, and the clinical history points to gestational origin.
• B. Complete mole shows swollen villi with trophoblastic hyperplasia confined to the uterus, not distant metastatic disease.
• C. Placental site trophoblastic tumor arises from intermediate trophoblast, produces low hCG with elevated human placental lactogen, and is less aggressive.
• E. Invasive mole shows molar villi invading the myometrium, not anaplastic trophoblast sheets without villi, and rarely causes distant lung metastases.

Distinguishing leiomyoma from leiomyosarcoma relies on histologic criteria rather than size or gross appearance: the number of mitoses per 10 high-power fields, combined with the presence of cytologic atypia and tumor cell necrosis, defines malignancy. Leiomyosarcoma typically shows more than 10 mitoses per 10 high-power fields along with significant nuclear atypia and necrosis, whereas leiomyoma has low mitotic activity and minimal atypia. Size alone is not diagnostic, since benign fibroids can be very large. This mitotic count criterion guides the pathologic diagnosis and prognosis.

• A. Large fibroids are common and benign; size alone does not indicate malignancy.
• C. Age is a risk factor for malignant transformation but is not a diagnostic histologic criterion.
• D. Both benign leiomyomas and some leiomyosarcomas can have a pseudocapsule, so this is not a reliable discriminator.
• E. LDH can be elevated in various conditions and is not a specific or standard criterion for distinguishing these tumors.

Endometriosis is defined by the presence of endometrial glands and stroma outside the uterine cavity, most often on the ovaries, uterosacral ligaments, and peritoneum. Ectopic endometrial tissue responds to cyclic hormonal changes, bleeding with each cycle, which causes cyclic pelvic pain, dyspareunia, and dysmenorrhea, and leads to the formation of ovarian endometriomas (chocolate cysts) filled with old, degraded blood. The resulting inflammation and adhesions are a common cause of infertility. Nodularity along the uterosacral ligaments on examination is a classic finding.

• A. A corpus luteum cyst is a single-cycle finding that typically resolves within weeks and does not cause chronic cyclic pain or infertility.
• B. Pelvic inflammatory disease presents with fever, cervical motion tenderness, and purulent discharge rather than cyclic pain tied to menses.
• C. Tubo-ovarian abscess presents with fever, purulent discharge, and an inflammatory adnexal mass, not cyclic pain with old blood on imaging.
• D. A dermoid cyst (mature cystic teratoma) contains heterogeneous fat, hair, or calcifications, not homogeneous old blood.

Adenomyosis is characterized by the presence of endometrial glands and stroma within the myometrium, at least one low-power field from the endometrial-myometrial junction. This ectopic endometrial tissue undergoes cyclic bleeding within the muscle wall, producing a diffusely enlarged, boggy, globular uterus and causing menorrhagia and dysmenorrhea, typically in multiparous women in their 40s. Imaging shows myometrial thickening with small cystic spaces rather than a discrete mass, distinguishing it from leiomyoma. Definitive diagnosis is made on hysterectomy specimen histology.

• A. Squamous metaplasia of endocervical glands is unrelated to the myometrial process causing diffuse uterine enlargement.
• B. Atypical glandular hyperplasia describes endometrial hyperplasia, a precursor to endometrial carcinoma, not adenomyosis.
• C. Glands within the fallopian tube wall describe a different and much rarer ectopic location, not the defining feature of adenomyosis.
• D. A well-defined pseudocapsule of smooth muscle describes leiomyoma, which presents as a discrete mass rather than diffuse enlargement.

A simple, thin-walled, unilocular anechoic cyst smaller than 5 to 7 cm in a young, reproductive-age woman is almost always a functional cyst (follicular or corpus luteal) and has a very low risk of malignancy. The appropriate next step is clinical and sonographic follow-up in 6 to 8 weeks to confirm spontaneous resolution, since most functional cysts resolve within one to two menstrual cycles. Surgery, tumor markers, or hormonal suppression are not indicated unless the cyst persists, enlarges, or develops concerning features such as septations or solid components. This conservative approach avoids unnecessary intervention in benign, self-limited disease.

• A. CA-125 lacks specificity in premenopausal women and is not indicated for a cyst with benign sonographic features.
• B. Surgery is reserved for cysts that persist, enlarge, or show suspicious features on imaging, not a simple cyst on first presentation.
• C. CT imaging adds radiation exposure without benefit when ultrasound has already characterized the cyst as simple and benign-appearing.
• D. Oral contraceptives do not accelerate resolution of existing functional cysts and are not used for this purpose.

Tamoxifen is a selective estrogen receptor modulator that acts as an antagonist on estrogen receptors in breast tissue, which is the basis for its use in treating and preventing estrogen receptor-positive breast cancer. However, it acts as a partial agonist on estrogen receptors in the endometrium, stimulating endometrial proliferation and increasing the risk of endometrial hyperplasia and endometrial carcinoma. Patients on tamoxifen therapy require monitoring and prompt evaluation of any abnormal uterine bleeding. This tissue-selective activity distinguishes tamoxifen from pure antiestrogens and from aromatase inhibitors.

• A. If tamoxifen were purely antagonistic in all tissues, it would not increase endometrial proliferation or cancer risk.
• B. Selective estrogen receptor degraders, such as fulvestrant, degrade the receptor; tamoxifen does not act through receptor degradation.
• D. Aromatase inhibition describes drugs like anastrozole and letrozole, not tamoxifen, which acts directly on the estrogen receptor.
• E. Tamoxifen's effects occur through direct estrogen receptor binding in peripheral target tissues, not through suppression of hypothalamic GnRH.

High-risk HPV types, such as 16 and 18, produce the oncoproteins E6 and E7, which drive malignant transformation. E6 binds and promotes degradation of p53, preventing apoptosis and DNA damage checkpoint arrest, while E7 binds and inactivates the retinoblastoma protein, releasing E2F transcription factors and driving uncontrolled progression through the cell cycle. The combined loss of these two tumor suppressor functions allows accumulation of genetic damage and progression from cervical intraepithelial neoplasia to invasive squamous cell carcinoma. This mechanism is the basis for HPV vaccination strategies targeting E6/E7-expressing high-risk genotypes.

• A. While E6 can influence telomerase indirectly, the defining oncogenic mechanism tested here is tumor suppressor degradation, not telomerase activation as the primary pathway.
• B. HPV oncoproteins do not primarily act by inhibiting mismatch repair; that mechanism is more characteristic of Lynch syndrome-associated cancers.
• C. HPV oncogenesis is driven by E6/E7 inactivation of tumor suppressors rather than direct activation of the RAS oncogene.
• D. E6 and E7 inactivate tumor suppressors rather than upregulate cyclin-dependent kinase inhibitors, which would restrain rather than promote cell cycle progression.

ASC-US with a positive high-risk HPV co-test indicates an increased likelihood of underlying cervical intraepithelial neoplasia, so colposcopy with directed biopsy is indicated to directly visualize the transformation zone and obtain tissue for histologic diagnosis. Colposcopy allows targeted sampling of acetowhite or abnormal vascular areas, avoiding both overtreatment and missed lesions. Excisional procedures like LEEP are reserved for confirmed high-grade dysplasia (CIN2/3) on biopsy, not as an initial diagnostic step. This triage strategy follows current ASCCP risk-based management guidelines.

• A. Repeating cytology without colposcopy would be appropriate only if HPV co-testing were negative.
• B. Routine screening in 3 years is inappropriate given the HPV-positive ASC-US result, which carries meaningful risk of dysplasia.
• C. LEEP is a treatment for biopsy-confirmed high-grade lesions, not a first-line diagnostic step after an ASC-US/HPV-positive result.
• D. Cold-knife conization is reserved for specific indications like suspected microinvasive disease or inadequate colposcopy, not initial triage.

CA-125 is a glycoprotein antigen expressed by coelomic epithelium-derived tissues and is elevated in over 80% of epithelial ovarian cancers, particularly the serous subtype. While not sensitive or specific enough for population screening due to elevation in benign conditions such as endometriosis and pelvic inflammatory disease, serial CA-125 measurements are the standard tool for monitoring treatment response and detecting recurrence after a baseline level is established. A rising CA-125 after treatment often precedes clinical or radiographic evidence of recurrence. AFP, beta-hCG, and inhibin are markers for other ovarian tumor types, not epithelial serous carcinoma.

• A. AFP is a marker for yolk sac tumors and some embryonal carcinomas, not epithelial ovarian carcinoma.
• B. Beta-hCG is elevated in choriocarcinoma and some germ cell tumors, not epithelial serous carcinoma.
• D. Inhibin B is a marker for granulosa cell tumors, not epithelial serous carcinoma.
• E. CA 19-9 is associated with pancreatic and some mucinous ovarian tumors, not typically serous carcinoma.

Granulosa cell tumors are sex cord-stromal tumors that secrete estrogen, producing unopposed estrogenic stimulation of the endometrium. In postmenopausal women this manifests as endometrial hyperplasia and abnormal uterine bleeding, as seen in this patient. Histologically these tumors show Call-Exner bodies, small follicle-like structures filled with eosinophilic fluid surrounded by granulosa cells. The combination of a unilateral solid ovarian mass with postmenopausal bleeding and endometrial hyperplasia strongly suggests a hormonally active granulosa cell tumor rather than a non-functioning epithelial or germ cell tumor.

• A. Krukenberg tumors are metastatic signet-ring cell tumors, typically bilateral, and not estrogen-secreting.
• B. Serous cystadenomas are benign epithelial tumors that do not secrete hormones and would not cause endometrial hyperplasia.
• C. Mature cystic teratomas (dermoid cysts) are germ cell tumors that are not hormonally active.
• E. Brenner tumors are benign transitional cell tumors that are generally hormonally inactive.

This presentation, a well-circumscribed, mobile, rubbery mass in a young woman that fluctuates in size and tenderness with the menstrual cycle, is classic for fibroadenoma, the most common benign breast tumor in women under 30. Fibroadenomas contain both stromal and glandular elements that retain estrogen and progesterone receptors, so they respond to cyclical hormonal fluctuations with transient stromal edema and glandular proliferation, causing premenstrual tenderness and size increase. This differs from fibrocystic change, which more typically causes diffuse nodularity and multiple areas of tenderness rather than a single discrete well-circumscribed mass. Fibroadenomas are benign and do not require excision unless symptomatic, enlarging, or diagnostically uncertain.

• A. The well-circumscribed, mobile, benign imaging characteristics and patient's young age argue strongly against malignancy.
• B. Apocrine metaplasia is a feature of fibrocystic change, but the described cyclical symptoms are hormonally mediated, not unrelated to hormones.
• C. There is no mention of fever, erythema, or purulent discharge to suggest infection, and infection would not show a well-circumscribed homogeneous mass on ultrasound.
• E. The cyclical nature of the symptoms directly correlates with hormonal fluctuation, not an independent inflammatory process.

The defining criterion separating ductal carcinoma in situ (DCIS) from invasive ductal carcinoma is whether the malignant cells have breached the basement membrane surrounding the duct. DCIS is confined by an intact basement membrane, confirmed by myoepithelial cell markers (p63, smooth muscle actin) or basement membrane stains, while invasive carcinoma shows malignant cells infiltrating the surrounding stroma with loss of the myoepithelial layer. This distinction determines staging (Tis vs T1+) and whether axillary lymph node metastasis is possible. Nuclear grade and necrosis help subclassify DCIS but do not determine invasiveness.

• A. Mitotic count reflects proliferative activity, not basement membrane breach.
• C. Nuclear grade helps classify DCIS subtype but does not determine whether invasion has occurred.
• D. Comedo necrosis indicates a high-grade DCIS pattern but is not the criterion for invasion.
• E. Lymphocytic infiltration is a nonspecific stromal reaction and not diagnostic of invasion.

Trastuzumab blocks HER2/neu receptors, which are expressed not only on tumor cells but also on cardiomyocytes, where HER2 signaling (activated by neuregulin-1) supports cell survival, repair, and adaptation to stress. Inhibition of this pathway impairs the heart's ability to compensate for stress, particularly after prior anthracycline exposure, leading to a reversible decline in ejection fraction rather than direct cytotoxic cell death. This cardiotoxicity is typically reversible upon discontinuation, unlike the dose-dependent, often irreversible cardiomyopathy caused by anthracyclines, which act through topoisomerase II and free radical-mediated mechanisms.

• A. Trastuzumab cardiotoxicity is not mediated by immune complex deposition in vessels.
• B. Trastuzumab's cardiotoxicity is not primarily immune-cell mediated cytotoxicity against myocytes.
• D. Free radical-doxorubicin complex formation describes anthracycline cardiotoxicity, not trastuzumab's mechanism.
• E. Mitochondrial DNA oxidative damage describes anthracycline toxicity, not trastuzumab's mechanism.

Paget disease of the breast presents with eczematous, crusting changes of the nipple-areolar skin caused by malignant epithelial cells (Paget cells) migrating along the lactiferous ducts into the epidermis. It is almost always associated with an underlying ductal carcinoma in situ or invasive ductal carcinoma, even when no palpable mass is present, so biopsy and imaging workup for breast carcinoma are mandatory. Unlike eczema, Paget disease is unilateral, does not improve with topical steroids, and shows malignant cells on biopsy. Paget cells are PAS-positive and express cytokeratin 7, helping distinguish them from melanoma.

• A. Intraductal papilloma presents with bloody nipple discharge, not eczematous skin change with malignant cells.
• C. Contact dermatitis would improve with topical steroids and would not show malignant cells on biopsy.
• D. Fat necrosis presents as a firm mass with history of trauma, not epidermal infiltration by malignant cells.
• E. Fibroadenoma is a benign stromal-epithelial tumor unrelated to nipple skin changes in Paget disease.

Inflammatory breast cancer results from invasion of dermal lymphatic channels by tumor cell emboli, which obstructs lymphatic drainage and produces the clinical triad of erythema, edema, and peau d'orange skin (from lymphatic obstruction causing skin edema around hair follicles). It is a clinical diagnosis supported by biopsy showing dermal lymphatic tumor invasion, not necessarily a palpable mass, and carries a poor prognosis due to its aggressive, highly metastatic behavior. It is often misdiagnosed as mastitis, but the absence of fever and lack of response to antibiotics should raise suspicion for malignancy.

• B. Duct ectasia causes nipple discharge and subareolar inflammation, not dermal lymphatic tumor emboli.
• C. Granulomatous mastitis shows noncaseating granulomas on histology, not tumor emboli in lymphatics.
• D. Bacterial mastitis would typically present with fever, purulent discharge, and response to antibiotics, and biopsy would show neutrophilic infiltration rather than tumor emboli.
• E. Fat necrosis presents as a firm, tender mass following trauma, not diffuse skin changes from lymphatic invasion.

Benign prostatic hyperplasia (BPH) characteristically arises in the transition zone, which surrounds the urethra, explaining the urinary obstructive symptoms seen with glandular and stromal hyperplasia. In contrast, prostatic adenocarcinoma most commonly arises in the peripheral zone, which is why early prostate cancer is often asymptomatic and classically detected as an irregular, firm nodule on digital rectal examination rather than causing urinary obstruction. This zonal difference also explains why BPH does not predispose to prostate cancer.

• A. The central zone is not the primary site for BPH; the transition zone is correct for BPH but the central zone is incorrect for cancer.
• B. The central zone is not the typical site of origin for prostatic adenocarcinoma.
• D. The central zone is an uncommon site for both BPH and adenocarcinoma.
• E. This reverses the correct zones for BPH and prostate cancer.

PSA is a serine protease produced by prostatic epithelial cells and is organ-specific but not cancer-specific; it can be elevated in benign prostatic hyperplasia, prostatitis, and other non-malignant conditions that disrupt the normal glandular architecture, in addition to prostate cancer. This lack of specificity for malignancy is why an elevated PSA alone cannot confirm a cancer diagnosis and why further evaluation (free-to-total PSA ratio, PSA velocity, biopsy) is often needed. PSA screening also carries a risk of overdiagnosis and overtreatment of clinically insignificant cancers.

• B. PSA is in fact produced by normal and neoplastic prostatic epithelial cells, which is why it is used as a marker.
• C. PSA can be elevated in localized, early-stage prostate cancer, which is the rationale for using it as a screening test.
• D. PSA is a stable serum marker that can be reliably measured and is used clinically for this reason.
• E. PSA tends to rise with age due to increasing prostate volume, not decrease.

Elevated AFP strongly suggests a yolk sac (endodermal sinu) tumor component, which is a nonseminomatous germ cell tumor histologically characterized by glandular and papillary structures resembling primitive yolk sac with Schiller-Duval bodies (glomerulus-like structures). Elevated beta-hCG indicates syncytiotrophoblastic differentiation, which can occur in choriocarcinoma or mixed germ cell tumors. Classic seminoma does not produce AFP and typically does not elevate beta-hCG significantly; it shows uniform cells with clear cytoplasm and lymphocytic infiltrate instead. The combination of markedly elevated AFP and hCG points toward a nonseminomatous (often mixed) germ cell tumor rather than pure seminoma.

• A. Pure choriocarcinoma elevates hCG markedly but does not typically cause the marked AFP elevation seen here.
• B. Call-Exner bodies are seen in granulosa cell tumors of the ovary, not testicular germ cell tumors.
• C. Sertoli cell tumors are sex cord-stromal tumors that do not produce AFP or hCG in this pattern.
• E. This describes classic seminoma, which does not produce AFP and is marker-negative in most cases.

This patient's presentation, sudden severe pain, absent cremasteric reflex, horizontal lie, and lack of relief with scrotal elevation (negative Prehn sign), is classic for testicular torsion, a surgical emergency caused by twisting of the spermatic cord that compromises testicular blood supply. Testicular salvage rates fall sharply after 6 hours of ischemia, so when clinical suspicion is high, immediate surgical exploration and detorsion with bilateral orchiopexy should proceed without delay for imaging. Doppler ultrasound is useful when the diagnosis is uncertain, but it should not delay surgery when the clinical picture is classic and time-sensitive.

• A. Ultrasound can be used in ambiguous cases but should not delay surgery when the clinical diagnosis is clear, given the time-sensitive nature of ischemia.
• B. Antibiotics would be appropriate for epididymitis or orchitis, which typically present with gradual onset and a positive Prehn sign, not acute torsion.
• D. Elective, delayed referral would result in testicular infarction and loss within hours in true torsion.
• E. NSAIDs and outpatient follow-up are inappropriate for a surgical emergency with ongoing testicular ischemia.

A varicocele is dilation of the pampiniform venous plexus due to venous reflux, classically described as a "bag of worms" on palpation. It is typically soft, collapses when the patient lies supine (as blood drains), and becomes more prominent with standing or Valsalva maneuver, which increases venous pressure. It does not transilluminate because it is not fluid-filled. Left-sided varicoceles are more common because the left gonadal vein drains at a right angle into the left renal vein, increasing resistance to flow.

• A. An inguinal hernia would typically present with bowel sounds or a mass extending into the inguinal canal, often with cough impulse, not a soft venous plexus collapsing supine.
• C. Testicular torsion presents acutely with severe pain and a high-riding, tender testis, not a chronic painless mass.
• D. A hydrocele is a fluid collection within the tunica vaginalis that transilluminates and does not change with position or Valsalva.
• E. A spermatocele is a discrete, painless, fluctuant cystic mass near the epididymal head, not a venous plexus that varies with position.

Chlamydia trachomatis is an obligate intracellular bacterium lacking a cell wall peptidoglycan layer usable for Gram staining, making Gram stain and culture-based methods insensitive and impractical for routine diagnosis. Nucleic acid amplification testing (NAAT) of endocervical, urine, or vaginal swab samples is the most sensitive and specific test and is the current standard for detecting C. trachomatis in suspected pelvic inflammatory disease. PID caused by C. trachomatis results from ascending infection from the cervix to the upper genital tract, causing cervical motion tenderness and adnexal tenderness as in this patient.

• A. Thayer-Martin agar is selective for Neisseria gonorrhoeae, not Chlamydia, which cannot be cultured on standard bacteriologic media.
• B. Wet mount is used to detect Trichomonas vaginalis motile trophozoites, not Chlamydia.
• D. Dark-field microscopy is used to detect Treponema pallidum in chancre fluid, not Chlamydia.
• E. Gram stain does not reliably detect Chlamydia because it is an obligate intracellular organism without a Gram-stainable cell wall.

This patient has disseminated gonococcal infection presenting as the classic triad of migratory polyarthritis (tenosynovitis), dermatitis (painless pustules), and, in some cases, purulent monoarthritis. Synovial fluid Gram stain and culture are frequently negative in disseminated gonococcal infection because organism burden in the joint is low; Neisseria gonorrhoeae is a fastidious, gram-negative diplococcus that is difficult to culture reliably from blood or joint fluid in this setting. Nucleic acid amplification testing of mucosal sites (cervix, urethra, pharynx, rectum) has much higher sensitivity for detecting N. gonorrhoeae in disseminated disease and is the preferred diagnostic approach.

• A. Blood cultures are often negative in disseminated gonococcal infection and are less sensitive than NAAT of mucosal sites.
• B. ANA testing is used to evaluate for systemic lupus erythematosus, not an infectious process.
• C. Repeating the Gram stain after centrifugation does not significantly improve sensitivity in disseminated gonococcal infection, where organism burden in joint fluid is characteristically low.
• E. Crystal analysis would evaluate for gout or pseudogout, not an infectious arthritis in this clinical context.

Nontreponemal tests (VDRL, RPR) detect antibodies against cardiolipin and can yield false positives in conditions such as systemic lupus erythematosus, antiphospholipid syndrome, pregnancy, and other infections. The fluorescent treponemal antibody absorption (FTA-ABS) test detects antibodies specific to Treponema pallidum antigens and is used as a confirmatory treponemal test after a positive nontreponemal screening test. This patient's history of a painless chancre (primary syphilis) that healed, now with a reactive RPR, is classic for syphilis, and FTA-ABS confirms the diagnosis with high specificity. Treponemal tests remain positive for life even after successful treatment, unlike nontreponemal titers which decline.

• A. VDRL on cerebrospinal fluid is used to evaluate for neurosyphilis, not to confirm the initial diagnosis of syphilis in this patient without neurologic symptoms.
• B. HIV testing may be appropriate for risk assessment but does not confirm the diagnosis of syphilis.
• C. Dark-field microscopy of blood is not useful; this test is performed on chancre or lesion exudate, not peripheral blood, and the lesion has already healed.
• D. Repeating RPR does not distinguish a true positive from a biologic false positive; a confirmatory treponemal-specific test is needed instead.

This patient's presentation of painful grouped vesicles and ulcers with fever and tender lymphadenopathy is characteristic of primary genital herpes caused by herpes simplex virus type 2 (HSV-2). A Tzanck smear of scrapings from the ulcer base classically shows multinucleated giant cells with eosinophilic intranuclear (Cowdry type A) inclusions, reflecting virus-induced cell fusion and nuclear changes. While viral culture or PCR is more sensitive and specific for confirming HSV, the Tzanck smear finding is a classic rapid bedside diagnostic clue tested on this topic.

• A. Motile flagellated organisms describe Trichomonas vaginalis on wet mount, not an ulcer scraping.
• B. Gram-negative intracellular diplococci are seen in gonococcal infection, not HSV.
• C. Spirochetes on silver or dark-field stain are characteristic of syphilis, which causes a painless, not painful, ulcer.
• D. Clue cells are seen in bacterial vaginosis, associated with Gardnerella vaginalis, not herpes ulcers.

This patient's frothy, malodorous discharge, elevated vaginal pH, vulvovaginal irritation, and "strawberry cervix" (punctate hemorrhages) are classic for Trichomonas vaginalis infection. T. vaginalis is a flagellated protozoan that is best identified on a saline wet mount, where motile, pear-shaped trophozoites with visible flagella can be seen under light microscopy. While NAAT has higher sensitivity, the wet mount is the classic rapid point-of-care test historically associated with this diagnosis and demonstrates the organism directly.

• A. Nontreponemal serology is used for syphilis screening, not for diagnosing trichomoniasis.
• C. KOH preparation is used to look for pseudohyphae in candidal vulvovaginitis, not motile protozoa.
• D. Gram stain does not reliably visualize motile protozoal trophozoites.
• E. Thayer-Martin agar selectively cultures Neisseria gonorrhoeae, not Trichomonas.

Combined oral contraceptives deliver exogenous estrogen and progestin that suppress hypothalamic GnRH pulsatility, which in turn lowers pituitary FSH and LH output. The resulting blunted FSH prevents selection and maturation of a dominant follicle, and the absent LH surge prevents ovulation even if a follicle develops. Progestin additionally thickens cervical mucus and thins the endometrium, but the dominant contraceptive mechanism is anovulation via negative feedback on the hypothalamic-pituitary axis. This negative feedback is the same principle exploited therapeutically by continuous GnRH agonists, just achieved through steroid feedback rather than receptor downregulation.

• B. OCPs do not act primarily through aromatase inhibition; that is the mechanism of drugs like anastrozole.
• C. Progestins in OCPs are progesterone receptor agonists, not antagonists; antagonism describes drugs like mifepristone.
• D. OCPs alter cervical mucus consistency to impede sperm transport but are not spermicidal.
• E. OCPs do not accelerate follicular atresia or apoptosis; they suppress gonadotropin-driven follicle development.

The estrogen component of combined oral contraceptives increases hepatic synthesis of several coagulation factors, including factors II, VII, IX, and X, and fibrinogen, while also modestly decreasing protein S. This shifts the hemostatic balance toward a hypercoagulable state, raising the risk of venous thromboembolism, particularly in the first year of use and in women with additional risk factors such as smoking or inherited thrombophilia. This is a dose-dependent effect of the ethinyl estradiol component rather than the progestin. Clinicians weigh this risk against the lower absolute VTE risk compared with pregnancy and the postpartum period.

• A. Progestins are not the primary driver of the procoagulant effect; thromboxane receptor upregulation is not the mechanism involved.
• C. Estrogen tends to increase, not suppress, PAI-1, which would further favor clot stabilization rather than explain the effect through suppression.
• D. Vasospasm and endothelial denudation describe mechanisms of other drugs such as cocaine, not OCP-related thrombosis.
• E. Estrogen does not transcriptionally silence antithrombin III as its main prothrombotic mechanism.

Leuprolide is a GnRH receptor agonist, but unlike endogenous GnRH, which is released in pulses, leuprolide is given continuously. Continuous occupancy of pituitary GnRH receptors causes an initial surge of LH and FSH release, which transiently increases testosterone, followed by receptor downregulation and desensitization. This leads to a sustained drop in LH and FSH secretion and subsequent suppression of testicular testosterone production to castration levels within about 2 to 4 weeks. Because of the initial testosterone flare, leuprolide is often co-administered with an androgen receptor antagonist in patients with bulky metastatic disease to prevent symptomatic tumor flare.

• A. 5-alpha-reductase inhibition describes finasteride and dutasteride, used for benign prostatic hyperplasia, not GnRH agonist therapy.
• C. Androgen receptor antagonism describes drugs such as bicalutamide or flutamide, not leuprolide's mechanism.
• D. Leuprolide acts upstream at the pituitary GnRH receptor, not directly on Leydig cell LH receptors.
• E. Aromatase inhibition is not the mechanism of leuprolide and is more relevant to breast cancer therapy with drugs like anastrozole.

Terbutaline is a beta-2 adrenergic receptor agonist that activates Gs proteins on myometrial smooth muscle, stimulating adenylate cyclase to increase intracellular cyclic AMP. Elevated cyclic AMP activates protein kinase A, which phosphorylates myosin light chain kinase and reduces its activity, lowers intracellular free calcium, and promotes calcium efflux and sequestration in the sarcoplasmic reticulum. The net effect is reduced actin-myosin cross-bridge cycling and myometrial relaxation, delaying preterm contractions. Common maternal adverse effects include tachycardia, tremor, and hyperglycemia due to systemic beta-adrenergic stimulation.

• A. Terbutaline does not act on oxytocin receptors; that mechanism describes atosiban, an oxytocin receptor antagonist used as a tocolytic in some countries.
• B. Phospholipase C and diacylglycerol signaling are not the primary pathway engaged by beta-2 agonists in the myometrium.
• D. Cyclic GMP-mediated relaxation describes the mechanism of nitric oxide donors, not beta-2 agonists.
• E. Terbutaline does not directly block calcium channels; that mechanism describes nifedipine, another tocolytic agent.