MRCOG Part 1: Endocrinology
Endocrinology is closely linked to Physiology and Biochemistry, covering hormonal regulation of the reproductive system and endocrine changes in pregnancy. Approximately 55 questions, with strong overlap with Physiology topics.
Topics Covered
Hypothalamic-Pituitary Axis
- ›GnRH — pulsatile release from hypothalamus, receptor downregulation with continuous exposure
- ›FSH and LH — glycoprotein hormones, pulsatility dependence
- ›Prolactin — inhibited by dopamine, elevated by TRH; causes of hyperprolactinaemia
- ›GH and IGF-1 — somatomedin hypothesis, acromegaly
- ›ADH (vasopressin) — osmotic regulation, SIADH vs diabetes insipidus
- ›Oxytocin — posterior pituitary, role in labour and lactation
Thyroid
- ›T3 and T4 — synthesis, iodine dependence, deiodinase conversion
- ›TBG increases in pregnancy — elevated total T4, free T4 remains normal
- ›Thyroid stimulating hormone (TSH) — first-line thyroid test
- ›Hypothyroidism in pregnancy — risk of miscarriage, preterm birth, neonatal effects
- ›Hyperthyroidism — Graves' disease (TSH receptor antibodies), management in pregnancy
- ›Fetal thyroid development — autonomous from 12 weeks, iodine importance
Adrenal & Glucose
- ›Cortisol — diurnal variation, CRH-ACTH-cortisol axis, Cushing's syndrome
- ›Aldosterone — RAAS, hypokalaemia, Conn's syndrome
- ›Adrenal medulla — catecholamines, phaeochromocytoma in pregnancy
- ›Insulin resistance in pregnancy — progesterone, cortisol, HPL contributions
- ›Gestational diabetes — diagnostic criteria (OGTT), risks to mother and fetus
- ›Diabetes in pregnancy — HbA1c, congenital anomalies, macrosomia
Exam Tips for Endocrinology
GnRH pulsatility is fundamental: pulsatile = FSH/LH secretion; continuous = downregulation (used therapeutically in GnRH analogues).
TBG and pregnancy: TBG rises → total T4 rises → TSH falls slightly in first trimester. Free T4 is what matters clinically.
Prolactin regulation: remember it is tonically inhibited by dopamine — drugs blocking dopamine (metoclopramide, antipsychotics) raise prolactin.
Gestational diabetes OGTT thresholds: fasting ≥5.6 mmol/L or 2-hour ≥7.8 mmol/L (NICE 2015 criteria).
Congenital anomalies in pre-existing diabetes (not gestational): neural tube defects, cardiac defects — related to periconceptional hyperglycaemia.
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