Explore the physical changes that occur during adolescence including puberty, growth spurts, hormonal changes, and development of secondary sexual characteristics.
Physical Changes in Adolescence
(Typically ages 10‑19; onset and timing vary by individual, sex, genetics, nutrition, and environment)
| Hormone | Source | Primary Action in Adolescence |
|---|---|---|
| Gonadotropin‑releasing hormone (GnRH) | Hypothalamus | Pulsatile release triggers pituitary secretion of LH & FSH. |
| Luteinizing hormone (LH) & Follicle‑stimulating hormone (FSH) | Anterior pituitary | Stimulate gonadal growth and sex‑steroid production. |
| Estrogen | Ovaries (girls) | Drives breast development, uterine growth, fat distribution, epiphyseal plate closure. |
| Testosterone | Testes (boys) | Promotes muscle mass, deepening voice, facial & body hair, spermatogenesis. |
| Growth hormone (GH) & IGF‑1 | Pituitary & liver | Accelerate linear growth (growth spurt). |
| Adrenal androgens (DHEA, DHEAS) | Adrenal cortex | Contribute to pubic/axillary hair and skin oiliness. |
The “pubertal clock” begins when GnRH pulses increase, typically around age 8‑9 in girls and 9‑10 in boys, but can vary by ±2‑3 years.
| Feature | Girls | Boys |
|---|---|---|
| Onset of growth spurt | 10‑12 yr (≈2 yr before menarche) | 12‑14 yr (≈2 yr after testicular enlargement) |
| Peak height velocity (PHV) | 8‑10 cm/yr (≈age 12) | 9‑11 cm/yr (≈age 14) |
| Final adult height | Usually reached 1‑2 yr after menarche | Reached 2‑3 yr after PHV; epiphyses close ~2 yr later |
| Body composition | ↑ body fat (especially hips & thighs) | ↑ lean muscle mass, ↓ body fat proportion |
| Sex | Change | Clinical Milestones |
|---|---|---|
| Female | Ovarian enlargement; onset of follicular activity; menarche (first menstrual bleed) | Menarche occurs ~2‑2.5 yr after thelarche (breast budding). |
| Male | Testicular enlargement (≥2.5 cm → puberty), epididymal growth, onset of spermatogenesis | First sperm in ejaculate appears ~6‑12 mo after testicular enlargement. |