The LH test is a blood test that measures the amount of luteinizing hormone (LH) produced by the pituitary gland. In men, LH stimulates the production of testosterone by the testes. In women, LH is one of the hormones involved in the monthly release of an egg from the ovaries.
Conditions that may call for LH evaluation in women include: amenorrhea, or absence of menstruationdelayed pubertyinfertility, which is the inability to become pregnantirregular menstrual cyclespelvic painprecocious pubertyvaginal bleeding without ovulation
A man may have an LH test if he has hypogonadism, or underdeveloped testes.
A blood sample is taken from a vein on the forearm or hand. First, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube, or tourniquet, is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them. A fine needle is gently inserted into a vein, and the tourniquet is removed. Blood flows from the vein through the needle and is collected in a syringe or vial. After the needle is withdrawn, the puncture site is covered with a bandage for a short time to prevent bleeding.
There is no preparation for an LH test. A woman's healthcare professional may request that the test be performed at a certain time in the woman's menstrual cycle. Recent exposure to a radioisotope during a nuclear medicine scan may interfere with test results.
Normal values for males are 7 to 24 U/L (units per liter) and for females 6 to 30 U/L.
Greater-than-normal levels of LH may be found in the following conditions in women: early onset of puberty, known as precocious pubertyKlinefelter's syndrome, a genetic disordermenopausepolycystic ovary diseasepremature failure of the ovaries caused by a genetic defect or related to radiation treatmentTurner's syndrome, a genetic disorder
Greater-than-normal levels of LH may be found in men with nonfunctioning testes, or absence of testes, called anorchia.
Lower-than-normal levels in women may indicate: anorexia nervosa, an eating disorderbreast-feedingbulimia, an eating disorderexercise-induced amenorrhea, or absence of menstruationinfertilityovarian cysts, or fluid-filled sacs on the ovariesthe use of oral contraceptives (birth control pills)
Lower-than-normal levels in men may be seen with: hypothalamic hypogonadism, which is caused by a disorder of the hypothalamusmultiple endocrine neoplasia, a genetic condition causing tumors of the endocrine glands