LH response to GnRH

Alternative names:

luteinizing hormone response to gonadotropin-releasing hormone

What the risks are:

• excessive bleeding
• fainting or feeling lightheaded
• hematoma (blood accumulating under the skin)
• infection (a slight risk any time the skin is broken)
• multiple punctures to locate veins

Special considerations:

GnRH (also called luteinizing hormone-releasing hormone, LHRH, or gonadotropin releasing hormone) is a peptide hormone secreted from the hypothalamus. GnRH stimulates the synthesis and release of LH (luteinizing hormone) and FSH (follicle-stimulating hormone). After puberty the secretion of GnRH, and also of LH and FSH, becomes pulsatile (rhythmic). However, continuous infusion of GnRH results in the inhibition of LH and FSH release.

In women, estrogen levels increase during the menstrual cycle until a level is reached at which a positive feedback signal stimulates GnRH and LH release; a phenomena that is responsible for the LH surge prior to ovulation. Progesterone in high concentrations (for example, during the luteal phase of the menstrual cycle or during pregnancy) decreases the frequency of GnRH pulsations and also the response of the pituitary to GnRH. In men, testosterone decreases the frequency of LH pulses, probably by a direct effect on GnRH release. Inhibin, a peptide produced by the testes and ovaries, is probably the major inhibitor of FSH release.

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.