Puberty

Puberty is the transition from childhood to reproductive maturity, driven by reactivation of the hypothalamic-pituitary-gonadal axis, with development of secondary sexual characteristics, a growth spurt, and attainment of fertility.

Hormonal events

• Reduced central inhibition and increased kisspeptin and neurokinin B signalling activate the GnRH pulse generator, first at night. Pulsatile LH and FSH rise, stimulating the gonads. Gonadal sex steroids drive secondary sexual characteristics.
• Adrenarche (age 6 to 8 in both sexes) is a separate process: adrenal DHEA and DHEAS secretion rises, causing pubic and axillary hair (pubarche) and adult-type body odour. It does not signify gonadarche.
• Growth hormone and IGF-1 increase with sex steroids, producing the pubertal growth spurt. Oestrogen (also in males via aromatisation) causes epiphyseal fusion.

Timing

• Girls: thelarche (breast budding, Tanner B2) at a mean age of about 10 years (range 8 to 13), menarche at about 12.5 years (2 to 2.5 years after thelarche), usually after peak height velocity.
• Boys: testicular enlargement to 4 mL or more (Tanner G2), mean age about 11.5 years (range 9 to 14), peak height velocity at about 13.5 to 14 years, and voice breaking at G4.
• Influences: genetics (about 50 to 80% of variance), nutrition and adiposity (earlier in overweight girls), chronic illness, endocrine-disrupting chemicals, psychosocial stress, and ethnicity. Secular trends show earlier thelarche.

Tanner staging

• Breast (B1 to B5), pubic hair (PH1 to PH5), genital (G1 to G5) and testicular volume (Prader orchidometer: 1 to 3 mL prepubertal, 4 mL and above pubertal, 20 to 25 mL adult).

Growth

• Peak height velocity: about 9 cm/year in girls (early in puberty, at B3) and 10 cm/year in boys (later at G4). Boys gain about 5 cm more adult height due to later onset and greater peak velocity.
• Bone mass accrues rapidly, and about 40 to 50% of adult peak bone mass is obtained during adolescence.

Disorders

• Precocious puberty (before 8 in girls and 9 in boys), delayed puberty (no breast development by 13 in girls and no testicular enlargement by 14 in boys), pubertal arrest, and variations (premature thelarche, premature adrenarche).

Normal sequence in girls

• Breast bud (B2), pubic hair, peak height velocity, menarche (at B4), then adult breast and hair pattern. Vaginal discharge (physiological leukorrhoea) occurs before menarche. Menstrual cycles are initially anovulatory and irregular for 1 to 2 years.

Normal sequence in boys

• Testicular enlargement, scrotal reddening, pubic hair, penile growth, spermarche (mean age 13 to 14), peak height velocity, voice change, facial hair, and axillary hair. Transient pubertal gynaecomastia occurs in 40 to 65% and usually resolves within 1 to 2 years.

Common concerns

• Acne, body odour, mood lability, growth discordance, delayed or early maturation, menstrual problems, gynaecomastia, and psychosocial effects (early maturing girls are at risk of body image concerns and early sexual activity, and late maturing boys of low self-esteem and bullying).

Assessment

• Growth chart (height, weight, BMI, height velocity), mid-parental height, family timing of puberty (menarche in mother, growth spurt in father), Tanner staging, testicular volume, bone age if growth or timing is abnormal, olfactory history, chronic illness, nutrition, exercise, medications, and psychosocial factors.

Red flags for pathological puberty: rapid progression, neurological symptoms (headache, visual changes), café-au-lait spots, abdominal or testicular mass, signs of virilisation in girls, failure of growth, anosmia, and syndromic features.

Normal puberty needs no investigations. Investigate when timing, tempo or sequence is atypical.

Assessment tools:

• Tanner stage by examination, with testicular volume by orchidometer.
• Bone age (left hand and wrist radiograph, Greulich-Pyle or Tanner-Whitehouse), advanced in precocious puberty and delayed in constitutional delay.
• Growth velocity over at least 6 months.

Biochemical evaluation:

• Basal LH (ultrasensitive assay, above 0.3 IU/L suggests pubertal activation), FSH, oestradiol, testosterone, DHEAS, 17-hydroxyprogesterone, TSH and free T4, prolactin, IGF-1.
• GnRH or GnRH agonist stimulation test when basal LH is equivocal (peak LH above 5 IU/L indicates central activation).
• hCG, AFP (germ cell tumours), and androgen assessment if peripheral precocity is suspected.

Imaging:

• Pelvic ultrasound (uterine length above 3.5 cm and volume above 2 mL, ovarian volume above 2 mL, endometrial line), testicular ultrasound, adrenal imaging.
• MRI of the hypothalamic-pituitary region for central precocious puberty in boys, girls under 6, rapid progression or neurological signs, and for hypogonadotropic hypogonadism.

Genetic testing: karyotype (Turner, Klinefelter), MKRN3, DLK1 (familial central precocious puberty), KISS1R, and panels for congenital hypogonadotropic hypogonadism.

Normal puberty

• Reassure, educate about physical changes, hygiene, menstruation, contraception, sexual health, nutrition and sleep. Vaccinate: HPV (9 to 14 years), meningococcal, Tdap. Anticipate acne with topical retinoids or benzoyl peroxide. Provide psychosocial support.

Variants

• Premature thelarche (isolated breast development under age 8, no growth acceleration or bone age advance): observe at 3 to 6 month intervals.
• Premature adrenarche: observe growth and bone age, exclude congenital adrenal hyperplasia by 17-hydroxyprogesterone, and monitor for metabolic risk.
• Pubertal gynaecomastia: reassure, as resolution is common. Tamoxifen 10 to 20 mg daily for persistent painful gynaecomastia, or surgery.

Precocious puberty: GnRH analogue (leuprolide 7.5 to 15 mg IM monthly or 11.25 to 30 mg every 3 months, triptorelin 3.75 to 11.25 mg, histrelin implant 50 mg yearly) for central precocious puberty. Treat the cause for peripheral disease.

Delayed puberty: constitutional delay: observation, or testosterone enanthate 50 to 100 mg IM monthly for 3 to 6 months in boys, low-dose oestradiol in girls. Permanent hypogonadism needs puberty induction.

Optimise puberty-linked health

• Calcium 1300 mg and vitamin D 600 to 1000 IU daily, weight-bearing activity, adequate nutrition, treatment of obesity and eating disorders, and iron screening in menstruating adolescents (ferrous sulfate 65 mg elemental iron daily for deficiency).
• Menstrual disorders: heavy menstrual bleeding (tranexamic acid 1 g three times daily for 4 days, combined oral contraceptive, NSAIDs), dysmenorrhoea (ibuprofen 400 mg every 6 to 8 hours, hormonal suppression), and polycystic ovary syndrome. Investigate primary amenorrhoea (no menses by 15 years or 3 years after thelarche).
• Sexual and reproductive health: contraception counselling (long-acting methods first-line), STI prevention, consent, and confidentiality.
• Mental health screening for depression, anxiety, eating disorders and substance use. Support for gender-diverse adolescents (see transgender health care).
• Growth: short stature assessment, and growth hormone for deficiency or Turner syndrome. Aromatase inhibitors (letrozole 2.5 mg daily) have been used off-label in boys to improve height prediction.

Follow-up

• Review growth and pubertal progress every 3 to 6 months when concerned, and refer to paediatric endocrinology for precocious or delayed puberty, abnormal tempo, or syndromic features.