TEXTBOOK ON PEDIATRIC GYNECOLOGY - 2013

Chapter 3. ANATOMICAL AND PHYSIOLOGICAL ASPECTS OF GIRLS' SEXUAL DEVELOPMENT

The SEXUAL DEVELOPMENT OF girls goes through several distinct periods: the intrauterine period, the neonatal period, the neutral period (from 1 to 7 years), the prepubertal period (from 7 years until the first menstruation — menarche), characterized by rapid growth, further Development of the reproductive Organs, the appearance of secondary sex characteristics, and the onset of the first menstruation (Phase I); and the pubertal period (from the first menstruation to 18 years), which culminates in the complete development of sex characteristics, deceleration of linear growth, and ovulatory menstrual cycles, preparing the body for reproductive function (Phase II). Each period features unique anatomical, morphological, and physiological characteristics.

STAGES OF A GIRL'S LIFE

According to the Classification by Yu. O. Krupko-Bolshova, several periods of a girl's sexual development are distinguished.

The prepubertal period extends from birth until the appearance of secondary sex characteristics.

The pubertal period spans from The Emergence of secondary sex characteristics to full biological maturity (18-19 years):

— early Puberty — from the appearance of secondary sex characteristics to menarche (10-14 years);

— proper puberty — the first 3 years following menarche, during which the Menstrual cycle becomes established, physical development concludes, and secondary sex characteristics are fully formed (14-16 years);

— late puberty — the phase during which the ovulatory cycle is established, and the hormone-producing function of the Ovaries closely approximates that of women of reproductive age (16-19 years).

The prepubertal period is marked by rapid growth, pelvic bone development, the emergence of secondary sex characteristics, further maturation of the reproductive organs, an increase in vaginal epithelial Cell layers, and the appearance of intermediate-type Cells. The hormonal function of the ovaries becomes active, accompanied by periodic estrogen peaks, though baseline levels remain low. This period concludes with menarche, a decrease in Growth Hormone levels, an elevation in gonadotropins and estrogens, and the activation of thyroid function. During prepuberty, an acyclic release of gonadotropins occurs, with minimal and episodic hypothalamic GnRH production; estradiol secretion is negligible, yet the feedback mechanism remains functional.

The early pubertal period is characterized by continued physical development in girls, particularly weight gain, pelvic development, and breast enlargement (thelarche). Vaginal epithelial cells begin nuclear pyknosis, the vaginal microflora undergoes Qualitative and quantitative shifts, and lactobacilli appear. Pubic Hair development initiates (pubarche), followed by the first menstruation (menarche) and the establishment of its rhythm. Growth hormone levels decline, while thyroid function remains active. Estrogen levels do not surge initially, and progesterone is present in trace amounts. Toward the end of this period, during the second post-menarcheal year, estrogen levels rise. The rhythm of gonadotropin secretion is established during early puberty.

The maturation process of hypothalamic structures intensifies, forming tight synaptic connections among cells that secrete Neurotransmitters and liberins (GnRH, somatoliberin, corticoliberin, thyroliberin). GnRH secretion assumes a rhythmic pattern, establishing a circadian (daily) rhythm that initially manifests exclusively during nocturnal Sleep. Driven by enhanced GnRH output, gonadotropin synthesis increases, and their release likewise becomes pulsatile. Elevated LH and FSH surges stimulate ovarian estrogen synthesis. The density of sex steroid receptors multiplies across all Cells of the Reproductive System, including the Hypothalamus and Pituitary gland, altering their sensitivity to estradiol. Achieving high Blood levels of estradiol acts as a trigger for a substantial gonadotropin surge, which completes follicular maturation and prompts ovulation. The first menstruation marks the Conclusion of the early pubertal period.

Proper puberty is characterized by the completion of breast development, pubic and axillary hair growth, which typically begins at age 13. The menstrual cycle transitions into an ovulatory pattern. This stage involves a quantitative increase in gonadotropin release and The formation of a cyclical secretory rhythm. A stable GnRH secretory rhythm is established, averaging once every hour. Consequently, LH and FSH secretion increases, driving enhanced ovarian estrogen synthesis. A positive feedback mechanism is formed: reaching a threshold level of E2 in the blood triggers the ovulatory surge of LH and FSH against the Background of a continuous circhoral secretory rhythm (Tables 1, 2).

Table 1. Centile values for physical development indicators in girls

Table 2. Centile values for external pelvic dimensions in girls

Early, middle, and late periods of adolescence are distinguished to reflect girls' individual developmental characteristics as distinct from chronological age.

To assess the degree of sexual maturity, the Tanner staging system is widely employed. In this classification, early puberty corresponds to stages I and II, middle puberty to stages III and IV, and late puberty to stage V of maturation (Table 3).

Secondary sex characteristics develop asynchronously during the prepubertal period: breast GROWTH AND DEVELOPMENT, as well as pubic hair growth, typically precede the appearance of axillary hair (Tables 4–6). The Development of secondary sex characteristics encompasses several stages of breast tissue formation:

M₀ — breast tissue is not palpable, the AREOLA is unpigmented;

M₁ — breast tissue is palpable within the BOUNDARIES OF THE areola, firm, and frequently tender;

M₂ — the nipple and areola are slightly elevated, and the breast assumes a conical shape;

M₃ — the breast is cone-shaped, with its base extending from the III to the VI rib, though the nipple does not project above the contour of the breast;

М₄ — the mammary gland is hemispherical in shape, theareola is pigmented, and the nipple rises above the areola; this is typically observed after 15 years of age.

Table 3. Stages of sexual development in girls

Table 4. Calculation of the sexual formula

Table 5. Standards of sexual development in schoolgirls

Table 6. Standards of puberty in girls (L. N. Ulanova et al., 1981)

Degrees of axillary hair growth:

Ах₀ — no hair growth;

Ax₁ — sparse straight hair;

Ах₂ — hair growth in the center of the axillae;

Ах₃ — hair growth across the entire axillary fossa.

Degrees of pubic hair growth:

Р₀ — no hair growth;

Р₁ — sparse straight hair;

Р₂ — hair growth in the central pubic area;

Р₃ — hair growth across the entire pubic area, with a horizontal upper border.

Sometimes, significant genital hair growth extending to the thighs and Perineum is observed. Such girls require special medical supervision (Table 7).

Table 7. Degree of hirsutism according to the Ferriman-Gallwey scale

To assess a woman's androgen status, the following concepts are used: the hirsutism score (Ferriman-Gallwey); the hormonal score (the sum of points reflecting the degree of body hair growth, excluding the forearms and lower legs); and the indifferent score (the sum of points reflecting the degree of hair growth on the forearms and lower legs).

Indices of a woman's androgen status

Normal hirsutism score: 1–7 points

Borderline hirsutism 8-11 scores

Hirsutism over 12 scores