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Luteinizing Hormone (LH)
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Panels › Hormone Panels › Luteinizing Hormone (LH)

Luteinizing Hormone (LH)

Significance
Luteinizing hormone (LH) is a glycoprotein gonadotropin with 29K–molecular weight produced by the anterior pituitary. The principle regulator of LH secretion is hypothalamic hormone called gonadotropin-releasing hormone or GnRH (also known as LH-releasing hormone) that acts on the anterior pituitary to bring about secretion of LH. Sex steroids also regulate secretion of GnRH and LH by negative feedback mechanisms. In women of reproductive age, luteinizing hormone affects key biochemical changes critical to normal menstrual and ovulatory function/events. LH stimulates the development and release of the egg from the ovary each month during the menstrual cycle. LH is critical not only to development/maturation of the ovarian follicle and production of progesterone in the theca cells, but also the follicular function after ovulation. Levels peak just prior to ovulation and this is referred to as the LH Surge. Normal patterns of gonadotropin secretion are necessary for reproduction, and impeding LH secretion is the approach used for contraception. Oral contraceptive pills contain a progestin (progesterone-mimicking compound), usually combined with an estrogen. Progesterone and estrogen inhibit LH secretion, and oral contraceptives are effective because they inhibit the LH surge that induces ovulation. In men, LH stimulates the testes to secrete testosterone. LH measurements are often used in conjunction with other tests (FSH, testosterone, estradiol and progesterone) for the workup of infertility in both men and women. LH levels are helpful in the investigation of menstrual irregularities and aid in the diagnosis of pituitary disorders. In children, FSH and LH are used to diagnose delayed and precocious (early) puberty. LH is also helpful in the diagnoses of polycystic ovary disease, premature ovarian failure, and menopause. Elevated blood levels of gonadotropins reflect lack of steroid negative feedback; where as excessive secretion of FSH and/or LH are most commonly due to gonadal failure or pituitary tumors.

Analysis
Determination of LH is performed by enzyme immunoassay.

Patient Preparation
Morning specimen is preferred. Where possible/appropriate avoid medication (steroid, ACTH, or gonadotropin medication etc) that can alter LH levels at least 48 hrs prior to specimen collection.

Specimen requirements
Serum specimen - from a plain redtop or a redtop gel (tiger top) tube. Separate serum from cells after centrifugation, if a plain redtop tube is used. Minimum volume required is 1 mL. Specimen should be kept refrigerated whenever possible.

Shipping Instructions
Ship specimen at ambient temperatures for shipments under 24 hrs. For longer shipments, ship with ice.

Additional information
http://www.labtestsonline.org/understanding/analytes/lh/test.html