The test for luteinizing hormone (LH), a hormone associated with reproduction and the stimulation of the release of an egg from the ovary (ovulation) in women and testosterone production in men.

In both women and men, LH is often used in conjunction with other tests (FSH, testosterone, estradiol and progesterone):

• In the workup of infertility

• To aid in the diagnosis of pituitary disorders that can affect LH production

• To help diagnose conditions associated with dysfunction of the ovaries or testicles

In women, LH levels are useful:

• In the investigation of menstrual irregularities

• To evaluate LH levels during the menstrual cycle; multiple urine LH tests may be ordered for this purpose. These LH "spot tests" can be performed at home and used to detect the surge in LH that indicates that ovulation will occur in the next 1-2 days. The tests can help determine when a woman is likely to be the most fertile.

In children, FSH and LH are used to diagnose delayed and precocious (early) puberty. Irregular timing of puberty may be an indication of a more serious problem involving the hypothalamus, the pituitary gland, the ovaries or testicles, or other systems. The measurement of LH and FSH may differentiate between benign symptoms and true disease. Once it is established that symptoms are a result of true disease, further testing can be done to discern the underlying cause.