Luteinizing hormone (LH) is produced by the pituitary gland. In
women, LH helps regulate the menstrual cycle and egg production (ovulation); in
men, LH stimulates the production of testosterone, which plays a role in sperm
Women's LH levels normally vary with the phase of the menstrual
cycle, rapidly increasing just before ovulation occurs. This "LH surge" is a
dependable sign that a woman is in a fertile time of her cycle. Men's LH levels
normally remain constant.
Abnormally high or low LH levels can be a sign of an inability to
produce eggs or sperm.