Luteinising hormone (LH) is produced by the anterior pituitary gland and plays a central role in reproduction in both sexes. In women, LH drives the final maturation of ovarian follicles and triggers ovulation — the LH surge is the signal that causes the egg to be released. After ovulation, LH stimulates the corpus luteum to produce progesterone, which prepares the uterine lining for a potential pregnancy.

In men, LH stimulates the Leydig cells in the testes to produce testosterone. Abnormal LH levels can indicate problems at the level of the pituitary gland, hypothalamus, or gonads. High LH with low sex hormones suggests primary gonadal failure, while low LH with low sex hormones suggests a pituitary or hypothalamic cause.