Luteinizing hormone (LH) is the brain’s go signal to the gonads. Released by the pituitary, it triggers ovulation in ovaries and drives testosterone production in testes. Through these sex steroids, LH influences fertility, menstrual rhythm, libido, muscle and bone maintenance, red blood cell production, mood, and metabolism.Patterns vary by sex and life stage. In cycling women, LH is low early, surges mid‑cycle to trigger ovulation, then moderates. In men, it remains fairly steady. It is very low before puberty, suppressed in pregnancy, and chronically high after menopause. Outside the ovulatory surge, mid‑range values generally indicate a well‑tuned axis.When LH is low, the brain‑pituitary drive is muted (hypogonadotropic hypogonadism). Ovaries may not ovulate and estrogen falls: irregular or absent periods, vaginal dryness, hot flashes, low bone density, and infertility. In men, testicular testosterone drops: low libido, erectile difficulty, fatigue, loss of muscle, anemia, and reduced sperm. In teens, puberty is delayed. Low LH is expected in pregnancy.When LH is persistently high, the pituitary is compensating for under‑responsive gonads (primary ovarian or testicular insufficiency): sex hormones fall and fertility declines; the postmenopausal pattern reflects this. A brief spike is normal at ovulation. Chronically higher LH relative to FSH can accompany polycystic ovary syndrome with irregular cycles and excess androgens. In children, high LH can signal early puberty.Big picture: LH is a real‑time readout of the hypothalamic–pituitary–gonadal axis. Because it governs estrogen and testosterone, it links to bone strength, body composition, metabolic and cardiovascular health, cognition, and lifelong reproductive capacity; pairing LH with FSH, estradiol or testosterone, prolactin, and thyroid tests clarifies where the axis is disrupted.
