Hormones
GnRH is released in pulses by the hypothalamus and tells the pituitary to release FSH and LH. Fertility medicines mimic or block it: GnRH agonists first stimulate and then switch off the pituitary, while GnRH antagonists block it quickly. Both are used in IVF to stop an early LH surge so egg collection can be timed accurately.
Also known as: gonadotrophin releasing hormone, GnRH hormone
Related South Africa guides
Sources
- ESHRE/ICMART glossary of assisted reproductive terminology
Last reviewed: 8 September 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.