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LH blood test

Definition

LH blood test measures the amount of luteinizing hormone (LH).

Alternative Names

How the Test is Performed

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

The health care provider may advise you to avoid drugs that may affect the test (see special considerations). For women in their reproductive years, the test may need to be done on a specific day of the menstrual cycle.

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 may be performed when a disorder associated with abnormal levels of LH is suspected.

LH is a protein hormone secreted by the anterior pituitary gland. In women, an LH surge at mid-cycle causes ovulation. For the next week or so, LH maintains the corpus luteum which synthesizes progesterone. If a woman does not become pregnant, the corpus luteum disintegrates after about 10 days. In men, LH stimulates production of testosterone by the Leydig cells of the testes.

Normal Results

• Normal adult male: 7 to 24 IU/L
• Normal adult female: 5 to 20 IU/L, with the midcycle peak about 3 times the base level

Note: IU/L = international units per liter

Normal values can be different depending on the lab and the test used. Ask your health care provider for the normal values for your test.

What Abnormal Results Mean

Greater-than-normal levels of LH may indicate:

• Anorchia (absence of testes or testes that do not function)
• Hypogonadism
• Klinefelter's syndrome
• Menopause
• Ovarian failure (see Ovarian hypofunction)
• Polycystic ovary disease
• Precocious puberty
• Turner's syndrome

Lower-than-normal levels of LH may indicate hypopituitarism.

Additional conditions under which the test may be performed include:

• Anovulatory bleeding
• Infertility
• Multiple endocrine neoplasia (MEN) I
• Ovarian cysts

Risks

• 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

Considerations

Recent exposure to radioisotopes -- a recent nuclear medicine scan, for example -- can interfere with test results. Drugs that can decrease LH measurements include birth control pills, hormone replacement therapy, and testosterone.

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.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.