LH response to GnRH

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LH response to GnRH

Definition:

LH response to GnRH is a test of the ability of the pituitary gland to appropriately respond to stimulation by a gonadotropin releasing hormone (GnRH, a hormone produced in the hypothalamus). This ability is assessed indirectly.

Alternative Names:

Luteinizing hormone response to gonadotropin-releasing hormone

How the test is performed:

A blood sample is drawn prior to an injection of GnRH. After a specified time, other blood samples are drawn so that LH can be measured.

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

For an infant or young child:

The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any continued bleeding.

How to prepare for the test:

Adults:

No special preparation is necessary.

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:

This test helps differentiate between primary (arising from the testicle or ovary) and secondary (originating in the hypothalamus or pituitary gland) hypogonadism. This test may be performed as part of the evaluation of gonadal failure associated with low testosterone levels in men or low estradiol (estrogen) levels in women.

Review Date: 8/8/2005
Reviewed By: Sharon Roseanne Thompason, M.D., M.P.H., Clinical Fellow, Department of Obstetrics & Gynecology, Brigham and Women's Hospital, Boston, MA. Review provided by VeriMed Healthcare Network.

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