Gynecology Topic 14. Puberty

I. Definition and Endocrine Basis

Definition

• Puberty: period when a child develops secondary sex characteristics and acquires reproductive capability.
• Normal onset: girls 8-13 years, boys 9-14 years.
• Timing is multifactorial: genetics, nutrition/body weight, chronic disease, environment and psychological factors.

Hypothalamic-Pituitary-Gonadal Axis

1. Hypothalamus

• Increased pulsatile GnRH secretion → activates puberty.

2. Anterior pituitary

• GnRH → FSH and LH release.
• FSH in female: follicular growth + granulosa aromatase → estrogen production.
• LH in female: theca androgen production; LH surge → ovulation; corpus luteum → progesterone.
• FSH in male: Sertoli cells → spermatogenesis.
• LH in male: Leydig cells → testosterone secretion.

3. Gonads and sex steroids

• Ovarian estrogen: breast development, uterine growth, female fat distribution, growth acceleration.
• Testosterone/DHT: genital growth, muscle/bone mass increase, voice deepening, facial/body hair.

II. Physical Changes in Girls

Normal Sequence

1. Adrenarche: increased adrenal androgens, about 6-8 years.
2. Gonadarche: HPG activation → ovarian estrogen production.
3. Thelarche: breast budding by estrogen, usually 9-11 years → first visible sign of female puberty.
4. Pubarche: pubic and axillary hair by adrenal androgens, usually 10-12 years.
5. Growth spurt / peak height velocity: GH + IGF-1 + estrogen → rapid height growth, around 12 years.
6. Menarche: first menstrual bleeding, average about 12-13 years; normal range about 10-15 years.

Terms and Early Cycles

• Gonadarche: activation of gonads by FSH/LH.
• Adrenarche: adrenal androgen rise.
• Thelarche: beginning of breast development.
• Pubarche: pubic/axillary hair development.
• Menarche: first menstrual bleed.
• Menarche usually occurs about 2-2.5 years after thelarche.
• Early cycles are often anovulatory because the HPG axis is still maturing.

III. Physical Changes in Boys and Tanner Stages

Normal Sequence in Boys

1. Adrenarche: adrenal androgen increase, often 7-9 years.
2. Gonadarche: HPG activation, usually 9-14 years.
3. Testicular enlargement: first visible sign; testicular volume > 4 mL suggests puberty.
4. Pubarche: pubic and axillary hair, usually 11-12 years.
5. Penile/scrotal growth, voice deepening, facial hair: later, about 13-14 years.
6. Spermarche: first sperm production/nocturnal emission, about 13-14 years.
7. Growth spurt: later than girls, often 13-15 years; GH, IGF-1 and testosterone.

Tanner Staging

• Tanner stage describes pubertal development of breast/genitalia and pubic hair.
• Breast/genital stage and pubic hair stage are assigned independently.

1. Stage 1: prepubertal; no pubic hair; no breast development; testes < 4 mL.
2. Stage 2: sparse/light pubic hair; breast bud in girls; testicular enlargement > 4 mL in boys.
3. Stage 3: darker/coarser pubic hair; further breast enlargement; penile lengthening and scrotal growth.
4. Stage 4: adult-type pubic hair limited to pubic area; areola forms secondary mound; penis length/width increase and glans enlargement.
5. Stage 5: adult pattern; pubic hair spreads to medial thighs; mature breast contour with flattened areola; adult genitalia/testes usually > 20 mL.

IV. Abnormal Timing: Exam Points

Precocious Puberty

• Definition: pubertal onset before 8 years in girls or before 9 years in boys.
• Main concern: accelerated growth + advanced bone age → premature epiphyseal closure → short adult stature.
• Central: early GnRH/HPG activation; peripheral: sex steroid production independent of HPG axis.
• Basic evaluation: history/exam, growth velocity, Tanner stage, bone age X-ray, FSH/LH/sex steroids ± imaging.
• Treatment: cause-specific; central idiopathic/pathologic cases may need GnRH agonist, e.g. leuprolide.

Delayed Puberty

• Definition: no secondary sex characteristics by 13 years in girls or 14 years in boys.
• Gynecologic threshold: no menarche by 15 years or within about 3 years after thelarche → evaluate primary amenorrhea.
• Hypergonadotropic hypogonadism: high FSH/LH → primary gonadal failure, e.g. Turner syndrome, primary ovarian insufficiency.
• Hypogonadotropic hypogonadism: low/normal FSH/LH → constitutional delay, chronic disease, undernutrition, hypothalamic/pituitary disease.
• Basic tests: FSH, LH, estradiol/testosterone, TSH, prolactin; imaging by context.