Foundations & the reproductive axis

First safety moves

• Reproductive-age pain, amenorrhoea or bleeding: exclude pregnancy before clever diagnosis.
• Acute pelvic pain plus positive pregnancy test means ectopic until safely excluded.
• Postmenopausal bleeding, shock, sepsis, torsion-like pain and sexual assault need urgent escalation.
• Examination requires consent, privacy, explanation and chaperone-sensitive practice.

Development map

• SRY working leads to testes; Sertoli cells make AMH and Leydig cells make testosterone.
• AMH removes Müllerian ducts; testosterone supports Wolffian ducts; DHT supports male external genitalia.
• Müllerian ducts form tubes, uterus, cervix and upper vagina; ovaries arise separately from the genital ridge.
• DSD reasoning uses three axes: chromosomes, gonad and phenotype.

CAH and DSD anchors

• Classic 21-hydroxylase CAH: low cortisol, high ACTH, high 17-OHP, high androgens.
• Salt-wasting CAH adds low aldosterone with hyponatraemia, hyperkalaemia and shock.
• Use DSD terminology and multidisciplinary counselling; do not rush non-urgent irreversible decisions.
• Uterus absent versus present often tells whether AMH worked.

HPO and follicle physiology

• Pulsatile GnRH stimulates FSH/LH; continuous GnRH agonist flares then suppresses.
• Sustained high estradiol causes positive feedback and the LH surge.
• LH acts on theca to make androgen; FSH acts on granulosa aromatase to make estradiol.
• High FSH with low estrogen localises hypogonadism to ovarian failure.

Steroid effects

• Estrogen builds proliferative endometrium and thin cervical mucus.
• Progesterone makes secretory endometrium, thick mucus and a small temperature rise.
• Progesterone withdrawal causes menses.
• Unopposed estrogen causes irregular bleeding, hyperplasia risk and cancer concern.