Luteinizing hormone (LH) blood test

Definition

The LH blood test measures the amount of luteinizing hormone (LH) in blood. LH is a hormone released by the pituitary gland, located on the underside of the brain.

Alternative Names

ICSH - blood test; Luteinizing hormone - blood test; Interstitial cell stimulating hormone - blood test

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

Your health care provider will ask you to temporarily stop medicines that may affect the test results. Be sure to tell your provider about all the medicines you take. These include:

• Birth control pills
• Hormone therapy
• Testosterone
• DHEA (a supplement)

If you are a woman of childbearing age, the test may need to be done on a specific day of your menstrual cycle. Tell your provider if you have recently been exposed to radioisotopes, such as during a nuclear medicine test.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

Why the Test is Performed

In women, an increase in LH level at mid-cycle causes release of eggs (ovulation). Your provider will order this test to see if:

• You are ovulating, when you are having trouble getting pregnant or have periods that are not regular
• You have reached menopause

If you are a man, the test may be ordered if you have signs of infertility or lowered sex drive. The test may be ordered if you have signs of a pituitary gland problem.

Normal Results

Normal results for adult women are:

• Before menopause: 5 to 25 IU/L
• Level peaks even higher around the middle of the menstrual cycle
• Level then becomes higher after menopause: 14.2 to 52.3 IU/L

LH levels are normally low during childhood.

Normal result for men over 18 years of age is around 1.8 to 8.6 IU/L.

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test result.

What Abnormal Results Mean

In women, a higher than normal level of LH is seen:

• When women of childbearing age are not ovulating
• When there is an imbalance of female sex hormones (such as with polycystic ovary syndrome)
• During or after menopause
• Turner syndrome (rare genetic condition in which a female does not have the usual pair of 2 X chromosomes)
• When the ovaries produce little or no hormones (ovarian hypofunction)

In men, a higher than normal level of LH may be due to:

• Absence of testes (anorchia) or testes that do not function
• Problem with genes, such as Klinefelter syndrome
• Endocrine glands that are overactive or form a tumor (multiple endocrine neoplasia)

In children, a higher than normal level is seen in early (precocious) puberty.

A lower than normal level of LH may be due to the pituitary gland not making enough hormone (hypopituitarism).

Risks

There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

• Excessive bleeding
• Fainting or feeling lightheaded
• Multiple punctures to locate veins
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

References

Jeelani R, Bluth MH. Reproductive function and pregnancy. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 26.

Lobo RA. Infertility: etiology, diagnostic evaluation, management, prognosis. In: Gershenson DM, Lentz GM, Valea FA, Lobo RA, eds. Comprehensive Gynecology. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 40.