Male Puberty: Stages and Timeline (Tanner Scale)

Male puberty follows the Tanner stages (G1–G5), typically starting 9–14 years (average 11.5).

Stage	Age Range	Key Changes
G1 (Prepubertal)	<9 yr	Childhood; no androgen effects.
G2 (Early)	10–12	Testicular enlargement (>2.5 cm / 4 mL); scrotal thinning/reddening; sparse pubic hair.
G3 (Mid)	12–14	Penile lengthening; further testicular growth; darker/coarser pubic hair; peak height velocity; voice deepening begins; spermarche (~13).
G4 (Late)	13–15	Penile widening; glans development; adult-type pubic hair (not medial thigh); facial hair starts; axillary hair; acne; voice deepens.
G5 (Adult)	15–17	Adult genitalia; full pubic hair (medial thigh); facial/body hair; growth plates fuse; fertility achieved.

Hormonal axis: GnRH → LH/FSH → Leydig cells (testosterone) + Sertoli cells (spermatogenesis, inhibin B). Adrenarche (DHEAS) precedes gonadarche — pubic/axillary hair, acne, body odor.

Variation is normal. Delayed (>14 no testicular growth) or precocious (<9) → endocrinology referral.