The simple idea (no memorising)
In childhood the brain–ovary axis is quiet. At puberty, the hypothalamus restarts its pulsing GnRH (Concept 5), the pituitary sends FSH/LH, the ovary makes estrogen, and the body matures.
The order matters — learn the words:
Loading diagram…
- Thelarche = breasts (an estrogen effect) — usually the first visible sign.
- Pubarche = pubic/underarm hair (an androgen effect) — a different hormone pathway.
- Menarche = the first period, arriving after breasts have developed.
Two clues that unlock later puzzles
- Breasts present = estrogen has been working. That single observation hugely narrows down "why no periods?" in the next concept.
- *Breast development and pubic hair run on different hormones* — which is exactly how we'll separate two look‑alike conditions (MRKH vs androgen insensitivity).
Early periods are often irregular at first — the axis is still tuning itself, so not every early cycle releases an egg.
When to look into it
Investigate delayed puberty if:
- no breast development by age 13, or
- no period by age 15 despite otherwise normal development.
Why it matters
Knowing the normal sequence and timing lets you spot what's off — and the "breasts = estrogen" clue is one of the most powerful shortcuts in all of gynaecology.
Quick check ✅
- What is usually the first visible sign of puberty, and which hormone drives it?
- By what ages should absent breasts, or an absent first period, be investigated?
Remember this 🌟
Where we're going next → What if the periods never start? A beautifully logical map awaits. Concept 35.