LH response to GnRH blood test: MedlinePlus Medical Encyclopedia

P 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.

T How the Test is Performed
P A blood sample is taken, and then you are given a shot of GnRH. After a specified time, more blood samples are taken so that LH can be measured.

T How to Prepare for the Test
P No special preparation is necessary.

T How the Test will Feel
P 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.

T Why the Test is Performed
P 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.
P This test is used to tell the difference between primary and secondary hypogonadism. Hypogonadism is 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.
P Depending on the type of hypogonadism:
- Primary hypogonadism starts in the testicle or ovary
- Secondary hypogonadism starts in the hypothalamus or pituitary gland
P This test may be also be done to check:
- Low testosterone level in men
- Low estradiol level in women

T Normal Results
P 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.

T What Abnormal Results Mean
P An increased LH response suggests a problem in the ovaries or testes.
P A reduced LH response suggests a problem with the hypothalamus gland or pituitary gland.
P Abnormal results may also be due to:
- Pituitary gland problems, such as release of too much hormone (hyperprolactinemia)
- Large pituitary tumors
- Decrease in hormones made by the endocrine glands
- Too much iron in the body (hemochromatosis)
- Eating disorders, such as anorexia
- Recent significant weight loss, such as after bariatric surgery
- Delayed or absent puberty (Kallmann syndrome)
- Lack of periods in women (amenorrhea)
- Obesity

T Risks
P Veins and arteries vary in size from one person 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.
P 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)

T Alternative Names
P Luteinizing hormone response to gonadotropin-releasing hormone

T References
P 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.
P 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.
P Haisenleder DJ, marshall JC. Gonadotropins. In: Jameson JL, De Groot LJ, de Kretser DM, et al, eds. Endocrinology: Adult and Pediatric. 7th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 116.

T Review Date 9/26/2015
P Updated by: Daniel N. Sacks MD, FACOG, obstetrics & gynecology in private practice, West Palm Beach, FL. Review Provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

