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What is Luteinizing Hormone, or LH?


Updated June 10, 2012

Definition: A hormone released from the pituitary gland in the brain that works with FSH (follicle stimulating hormone) to recruit and stimulate an egg follicle to grow each month. Once an egg is mature, levels of LH surge, triggering estrogen to fall and ovulation to occur. Over-the-counter ovulation predictor kits (OPKs) look for this surge in LH to predict ovulation.

A combination of FSH and LH, or LH alone, is sometimes used by fertility specialists to stimulate the ovaries to produce follicles for IVF (in vitro fertilization) or IUI ( intrauterine insemination). These are injectable medications known as Luveris and Menopur.

Women with PCOS sometimes have persistently elevated levels of LH. This may make testing for ovulation using an OPK difficult. If you are having trouble detecting a surge or are getting consistently positive results regardless of the point you are at in your cycle, see your physician or a specialist for assistance.

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