Luteinising Hormone (LH) is a hormone produced by the pituitary gland that plays a crucial role in male and female fertility. In females, LH levels increase sharply around the middle of the menstrual cycle, causing ovulation to occur. It is also responsible for the formation of the corpus luteum, which produces progesterone to prepare the uterus for pregnancy. In males, LH stimulates the production of testosterone in the Leydig cells of the testes, which is essential for the development of male reproductive organs and secondary sexual characteristics.