Classification of the transitional period
The transitional period is divided into several consecutive stages, each having its own clinical features:
- Premenopause: begins in women over 45–47 years of age. At this time, the first climacteric symptoms appear (metabolic-endocrine, psycho-emotional, and neurovegetative). The stage ends with the complete cessation of menstruation.
- Menopause (from Greek words menos — month, pauses — end): the last spontaneous menstruation in a woman's life. Important nuance: this diagnosis is established exclusively retrospectively, based on anamnestic data.
- Postmenopause: is stated if menstruation has been absent for 12 months or more. It is divided into early (first two years) and late (lasting more than two years).
- Perimenopause: a collective term that combines all of premenopause and the first two years of postmenopause.
Neuroendocrine shifts
Key transformations affect the hypothalamic-pituitary-ovarian system.
At the level of central regulation, the hypothalamus loses its former sensitivity to estrogens, and the secretion of gonadotropin-releasing hormone loses its normal pulsatile (circhoral) rhythm. In response, the pituitary gland sharply increases the synthesis of gonadotropins: follicle-stimulating hormone (FSH) increases 14-fold, and luteinizing hormone (LH) increases 3-fold.
In the ovaries during premenopause, inhibin production drops, and follicles become resistant to the action of gonadotropins. Corpus luteum insufficiency gradually forms, and the number of anovulatory cycles progressively increases. The follicular reserve is depleted, and the cessation of cyclic function coincides with the onset of menopause.
In postmenopause, the hormonal profile changes cardinally:
- Progesterone completely ceases to be produced.
- Total estrogen secretion decreases, and their ratio changes.
- The dominant hormone becomes estrone — the least active estrogen fraction. Its concentration in blood plasma is 3–4 times higher than the estradiol level.
- Estrone is produced extragonadally: via peripheral conversion from androstenedione in muscle and adipose tissue. Androstenedione itself is secreted predominantly by the adrenal glands and to a lesser extent by the ovaries.
Uterine and endometrial involution
The described hormonal shifts trigger the involution of reproductive organs. Notably, in premenopause, the macrostructure and dimensions of the uterus remain the same as in reproductive age.
In postmenopause, the uterus, being a target organ for sex steroids, loses an average of a third of its volume due to atrophy processes in the myometrium. The maximum intensity of atrophy is observed in the first 2–5 years, and 20 years later the organ dimensions finally stabilize.
Ultrasonic picture of the myometrium:
- Echogenicity gradually increases as the duration of postmenopause increases.
- Multiple hyperechoic areas appear, corresponding to zones of fibrosis.
- On dopplerography, blood flow becomes extremely scant and is registered exclusively in the peripheral layers.
Endometrial changes (M-echo): The mucous membrane of the uterus ceases to undergo cyclic changes and undergoes profound atrophy. The longitudinal and transverse dimensions of the uterine cavity decrease. Normally, the anteroposterior dimension of the M-echo decreases to 4–5 mm or less, and its echogenicity increases.
In prolonged postmenopause, marked atrophy can lead to the formation of synechiae (adhesions), which are visualized on ultrasound as small linear inclusions of increased echogenicity. Serometra is also considered a norm — the accumulation of a small amount of fluid (anechoic strip on ultrasound). It occurs due to age-related overgrowth of the cervical canal, which prevents the natural outflow of contents.
Ovarian changes
Ovaries in postmenopause also undergo involution: their linear dimensions and total volume decrease, and the echostructure changes completely.
Two main types of ovarian structure are distinguished during this period:
- Atrophic type.
- Hyperplastic type.
The atrophic type is characterized by a significant decrease in the size and volume of the organ, as well as a decrease in its sound transmission during ultrasound examination. Hyperechoic areas appear in the ovarian structure, indicating the predominance of the connective tissue component over the glandular one.
'E' rule for the postmenopausal hormonal profile: Estradiol drops, Estrone becomes dominant, which is synthesized extragonadally (in adipose and muscle tissue).
Class and exam questions
How to accurately determine the date of onset of menopause?
The date of menopause can be established exclusively retrospectively. The diagnosis is made only after spontaneous menstruation has been absent for 12 consecutive months.
Is fluid in the uterine cavity in postmenopause a sign of pathology?
No, the accumulation of a small amount of fluid (serometra) against the background of a thin atrophic endometrium is not a pathology. This condition occurs due to age-related narrowing or overgrowth of the cervical canal, which prevents the outflow of contents.
Do the sizes of the uterus and ovaries change in premenopause?
During the premenopause period, significant changes in the macrostructure and dimensions of the uterus and ovaries compared to reproductive age do not yet occur. Active involution begins later.
What else to study on this topic
- Neurovegetative and psycho-emotional symptoms of premenopause
- Mechanisms of peripheral conversion of androgens to estrone
- Ultrasound signs of the hyperplastic type of ovaries
- Formation of intrauterine synechiae against the background of endometrial atrophy
- Dopplerography of uterine blood flow in postmenopause
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