LH response to GnRH blood test

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Definition

LH response to GnRH is a blood test to help determine if your pituitary gland can correctly respond to gonadotropin releasing hormone (GnRH). LH stands for luteinizing hormone.

Alternative Names

Luteinizing hormone response to gonadotropin-releasing hormone

How the test is performed

A blood sample is taken, and then you are given an shot of GnRH. After a specified time, more blood samples are taken so that LH can be measured.

How to prepare for the test

No special preparation is necessary.

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 sensation. Afterward, there may be some throbbing or a slight bruise. These soon go away.

Why the test is performed

GnRH is a hormone made by the hypothalamus gland. LH is made by the pituitary gland. GnRH causes (stimulates) the pituitary gland to release LH.

This test is used to tell the difference between primary and secondary hypogonadism. Hypogonadism a condition in which the sex glands make little or no hormones. In men, the sex glands (gonads) are the testes. In women, the sex glands are the ovaries.

Depending on the type of hypogonadism:

  • Primary hypogonadism starts in the testicle or ovary
  • Secondary hypogonadism starts in the hypothalamus or pituitary gland

This test may be also be done to check:

Normal Values

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

An increased LH response suggests a problem in the ovaries or testes.

A reduced LH response suggests a problem with the hypothalamus gland or pituitary gland.

Abnormal results may also be due to:

What the risks are

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 related to having blood drawn are rare but may include:

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

Special considerations

References

Borawski D, Bluth MH. Reproductive function and pregnancy. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, Pa: Elsevier Saunders;  2011:chap 25.

Gruber HA, Farag AF. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry’s Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 24.

Melmed S, Kleinberg D, Ho K. Pituitary physiology and diagnostic evaluation. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, Pa: Elsevier Saunders; 2011: chap 8.

Version Info

  • Last reviewed on 9/30/2013
  • 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, Bethanne Black, and the A.D.A.M. Editorial team.

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This page was last updated: April 14, 2014

         
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