Luteinising Hormone (LH)
A gonadotropin hormone produced by the anterior pituitary that triggers ovulation in women and stimulates testosterone production in men. LH release is controlled by pulsatile GnRH signalling. GnRH agonists and antagonists exert their therapeutic effects by modulating LH secretion.
Technical Context
LH is a heterodimeric glycoprotein (α subunit shared with FSH, TSH, hCG; unique β subunit). In women, the LH surge triggers ovulation — a rapid rise in LH causes follicular rupture and oocyte release approximately 36 hours after the surge begins. In men, LH stimulates Leydig cells to produce testosterone. The GnRH pulse frequency differentially regulates LH vs FSH synthesis: high-frequency pulses (every 60 minutes) favour LH-β transcription, while low-frequency pulses (every 2-4 hours) favour FSH-β. Continuous GnRH exposure suppresses LH within 1-2 weeks through gonadotroph GnRH receptor downregulation. GnRH antagonists produce immediate LH suppression. LH measurement is clinically important for confirming suppression during GnRH-based therapies.