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.
Who is a candidate for the test?
Conditions that may call for LH evaluation in women include:
- amenorrhea, or absence of menstruation
- delayed puberty
- infertility, which is the inability to become pregnant
- irregular menstrual cycles
- pelvic pain
- precocious puberty
- vaginal bleeding without ovulation
A man may have an LH test if he has hypogonadism, or underdeveloped testes.
How is the test performed?
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 After the needle is withdrawn, the puncture site is covered with a bandage for a short time to prevent bleeding.
What is involved in preparation for the test?
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.
What do the test results mean?
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 puberty
- Klinefelter's syndrome, a genetic disorder
- polycystic ovary disease
- premature failure of the ovaries caused by a genetic defect or related to radiation treatment
- Turner'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 disorder
- bulimia, an eating disorder
- exercise-induced amenorrhea, or absence of menstruation
- ovarian cysts, or fluid-filled sacs on the ovaries
- the 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 hypothalamus
- multiple endocrine neoplasia, a genetic condition causing tumors of the endocrine glands