Luteinizing hormone (LH) is a hormone produced by the pituitary gland in the brain. It plays a crucial role in regulating the reproductive system in both males and females. In women, LH triggers ovulation, the release of an egg from the ovary, and helps maintain the menstrual cycle. In men, it stimulates the production of testosterone, which is essential for sperm production. LH levels fluctuate throughout the menstrual cycle in women, peaking just before ovulation. In men, LH levels remain relatively stable but are important for overall reproductive health. Abnormal LH levels can indicate various health issues, including fertility problems.