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LH blood test
Definition
The LH blood test measures the amount of luteinizing hormone (LH). LH is a hormone released by the pituitary gland.
In women, an increase in LH levels at mid-cycle causes ovulation.
In men, LH stimulates production of testosterone.
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. For information on how this is done, see: Venipuncture
How to Prepare for the Test
The health care provider may advise you to avoid drugs that may affect the test. Drugs that can decrease LH measurements include birth control pills, hormone replacement therapy, and testosterone.
If you are a woman of childbearing age, the test may need to be done on a specific day of your menstrual cycle.
How the Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the Test is Performed
Your doctor may order this test if you are a woman who is having trouble getting pregnant, who does not have regular periods, or has signs of a disorder associated with abnormal levels of LH.
Normal Results
A normal result for am adult female is 5 to 25 IU/L. Levels peak around the middle of the menstrual cycle.
The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
What Abnormal Results Mean
Greater-than-normal levels of LH may indicate:
- Anorchia (absence of testes or testes that do not function)
- Hypogonadism
- Klinefelter syndrome
- Menopause
- Ovarian failure (see Ovarian hypofunction)
- Polycystic ovary disease
- Precocious puberty
- Turner syndrome
Lower-than-normal levels of LH may indicate hypopituitarism.
Additional conditions under which the test may be performed include:
Risks
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample 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 light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Considerations
Recent exposure to radioisotopes (a recent nuclear medicine scan, for example) can interfere with test results.
References
Webster RA. Reproductive function and pregnancy. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa: Saunders Elsevier; 2006:chap 25.
Ferri FF. Laboratory tests and interpretation of results. In: Ferri FF, ed. Ferri’s Clinical Advisor 2012. 1st ed. Philadelphia, Pa: Mosby Elsevier; 2011:section IV.
Reviewed By: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine; Susan Storck, MD, FACOG, Chief, Eastside Department of Obstetrics and Gynecology, Group Health Cooperative of Puget Sound, Bellevue, Washington; Clinical Teaching Faculty, Department of Obstetrics and Gynecology, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
