Reproductive Endocrinology and Infertility
Reproductive endocrinology questions usually start with the WHO classification of anovulation: group I is hypothalamic-pituitary failure with low gonadotrophins, group II is normogonadotrophic with polycystic ovary syndrome the commonest cause, and group III is hypergonadotrophic ovarian failure. PCOS is diagnosed by two of three Rotterdam criteria - oligo-ovulation, clinical or biochemical hyperandrogenism, and polycystic ovaries on ultrasound - after excluding thyroid disease, hyperprolactinaemia and congenital adrenal hyperplasia.
Letrozole is first-line ovulation induction, especially in PCOS, and gives higher live birth rates than clomiphene. Gonadotrophins are used in clomiphene resistance and require monitoring for ovarian hyperstimulation syndrome; preventive strategies include antagonist protocols, GnRH agonist triggers and freeze-all. Endometriosis is diagnosed laparoscopically and treated medically or surgically according to fertility goals. Male factor is assessed with semen analysis against WHO reference limits.
Traps: diagnosing PCOS on ultrasound alone; forgetting that premature ovarian insufficiency requires FSH above 25 mIU/mL on two occasions at least four weeks apart in a woman under 40; investigating recurrent pregnancy loss after a single loss; and missing hyperprolactinaemia or thyroid dysfunction as a cause of amenorrhoea.
Rule of thumb: anovulatory infertility in PCOS starts with letrozole, not clomiphene.