Luteinizing hormone – is one of the main hormones that plays a major role in controlling the reproductive system in both men and women. In men, LH signals the testes to produce testosterone, which in turn, stimulates sperm production. In women, LH performs different roles at different stages of the menstrual cycle. Initially to produce the female sex hormone estradiol. Latterly LH stimulates the production of progesterone, which is required to support the early stages of pregnancy, if fertilization occurs. Used in the assessment of amenorrhea, irregular menstrual periods infertility, lack of ovulation, and identify polycystic ovary syndrome (PCOS).