Hypopituitarism (Pituitary Insufficiency)
Develops upon destruction or compression of adenohypophysis tissue. The main forms include:
- Postpartum necrosis (Sheehan's syndrome). Occurs due to impaired blood flow during massive blood loss in childbirth. Due to the absence of the blood-brain barrier in the pituitary gland, abnormal proteins enter the bloodstream, which provokes low-grade autoimmune inflammation.
- Pituitary cachexia (Simmonds' syndrome). An acute condition against the background of sepsis, trauma, or tumors, in which over 90% of secretory cells die. Deficiency of all tropic hormones (panhypopituitarism) leads to rapid weight loss (by 20–25 kg in the first month).
- Empty sella syndrome. Pathology associated with a defect of the sella diaphragm. Cerebrospinal fluid pressure causes atrophy and sclerosis of the organ.
- Suprasellar tumors. The most well-known is craniopharyngioma (growing from Rathke's pouch remnants). In children, it causes growth and puberty retardation, and in adults, hypogonadism and "white addisonism" (adrenal insufficiency without skin hyperpigmentation).
Hyperpituitarism and types of adenomas
Hormone excess is most often caused by adenomas. By diameter, they are divided into microadenomas (up to 10 mm) and macroadenomas (10 mm and more). A reliable diagnosis is made only based on electron microscopy and immunohistochemistry results.
- Prolactin-secreting adenoma. The most common (microadenoma from chromophobic cells). Leads to infertility, decreased libido, and in women, galactorrhea and amenorrhea.
- Somatotropic adenoma. Caused by a GSA protein mutation. In children, it provokes gigantism, and in adults, acromegaly. Patients experience enlargement of the hands, feet, jaws, and tongue (macroglossia). Arterial hypertension, steroid diabetes, immunodeficiency, and early atherosclerosis develop (due to an increase in LDL, VLDL, and ketone bodies).
- Corticotropic adenoma. A basophilic tumor producing ACTH. Triggers Cushing's disease (upper-body obesity with thin limbs, striae, osteoporosis, hypertension).
- Gonadotropic and thyrotropic adenomas. Rare, causing hypogonadism and hyperthyroidism (with a risk of neck tissue compression), respectively.
Posterior pituitary pathology
Posterior lobe diseases are diagnosed rarely and are associated with impaired secretion of antidiuretic hormone (ADH).
- Diabetes insipidus. Develops with ADH deficiency against the background of tumors, infections, or trauma. The main symptoms are severe thirst and the excretion of huge volumes of hypoosmolar urine (more than 3 liters per day). Secondary diabetes insipidus is possible in liver and kidney diseases (the sites of ADH inactivation).
- Hyperhydropexic syndrome (Syndrome of inappropriate antidiuretic hormone secretion - SIADH). The opposite condition caused by ADH excess. Characterized by generalized edema, oliguria, decreased blood sodium levels, and water intoxication (headaches, nausea).
Malignant pituitary tumors
Pituitary carcinomas account for only about 1% of all organ neoplasms.
- As a rule, they are hormonally inactive.
- Microscopically, they consist of small chromophobic cells with polymorphic nuclei and a high mitotic rate.
- Reliably confirming malignancy is often possible only after detecting metastases.
- Carcinomas metastasize predominantly within the skull (spread to bones, liver, or lymph nodes is extremely rare).
Briefly: answers to topical questions
What is the difference between Cushing's disease and Cushing's syndrome?
The main difference lies in the localization of the primary pathological process and the blood level of adrenocorticotropic hormone (ACTH).
| Sign | Cushing's disease | Cushing's Syndrome |
|---|---|---|
| Localization | Pituitary tumor; corticotropic adenoma produces ACTH and stimulates the adrenal glands | The primary process is localized in the adrenal gland: corticosterone-producing adenoma (corticosteroma) or adrenal cortex hyperplasia; ectopic ACTH secretion and iatrogenic syndrome with prolonged corticosteroid administration are also described |
| ACTH level | High | In primary adrenal pathology, it is usually decreased via negative feedback |
| Glucocorticoid level | High | High |
What types of secretory cells are distinguished in the adenohypophysis, and what hormones do they produce?
In sources, adenohypophysis cells are classified according to the staining (tinctorial) properties of the cytoplasm:
- Chromophobic cells — poorly stained; according to main data, they do not secrete hormones, though a number of authors suggest their involvement in ACTH synthesis.
- Basophilic cells — stain with basic dyes; corticotropic adenoma consists of large basophilic cells and is associated with ACTH production.
- Acidophilic / eosinophilic cells — stain with acidic dyes; somatotropic adenoma consists of large eosinophilic cells and is associated with GH production.
- Cells with lobulated nuclei — a small population of 2–5%; their tinctorial properties can change, with a constant feature being the lobulated nuclear structure.
Also, sources indicate hormone-active adenomas of the adenohypophysis: prolactinoma produces prolactin, gonadotropic adenoma is associated with elevated FSH and less frequently LH, and thyrotropic adenoma causes hyperthyroidism.
What immunohistochemical markers are used to verify the type of pituitary adenoma?
To verify the type of pituitary adenoma during immunohistochemical examination, markers for specific hormones contained in the cytoplasmic secretory granules of the cells are used.
Depending on the type of tumor, the expression of the following hormones is detected:
- Prolactin (in prolactin-secreting adenomas);
- ACTH (adrenocorticotropic hormone);
- GH (growth hormone / somatotropic hormone);
- LH (luteinizing hormone);
- FSH (follicle-stimulating hormone);
- TSH (thyroid-stimulating hormone).
The components of Wolfram syndrome are easy to remember by the English acronym DIDMOAD: Diabetes insipidus, Diabetes mellitus, Optic atrophy, and Deafness.
Class and exam questions
What is the difference between pituitary microadenomas and macroadenomas?
The classification is based on tumor size: microadenomas have a diameter of up to 10 mm, and macroadenomas are 10 mm and larger. Moreover, macroadenomas can fill the entire sella turcica.
Why does autoimmune damage develop in Sheehan syndrome?
Tissue necrosis leads to the appearance of abnormal proteins in the blood. Since there is no blood-brain barrier in the pituitary gland, the immune system reacts to them and triggers autoimmune inflammation.
What appearance is typical for a patient with a corticotroph adenoma?
Cushing's disease develops: progressive obesity of the face and torso against the background of disproportionately thin limbs (due to muscle atrophy), as well as purplish striae on the skin.
What else to study on this topic
- Mechanism of secondary immunodeficiency development in somatotropic adenoma
- Differential diagnosis of adenoma types using electron microscopy
- Histological differences between chromophobic, basophilic, and eosinophilic pituitary cells
- Effect of hypopituitarism on lipid and carbohydrate metabolism
- Pathogenesis of impaired glucose tolerance in hyperhydropexic syndrome
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