LH blood test; Luteinizing hormone
LH blood test measures the amount of luteinizing hormone (LH).
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 a tourniquet (an elastic band) is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet 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 tourniquet 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.
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.
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child’s age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child’s age:
- Infant test or procedure preparation (birth to 1 year)
- Toddler test or procedure preparation (1 to 3 years)
- Preschooler test or procedure preparation (3 to 6 years)
- Schoolage test or procedure preparation (6 to 12 years)
- Adolescent test or procedure preparation (12 to 18 years)
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 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
What abnormal results mean
Greater-than-normal levels of LH may indicate:
- Anorchia (absense of testes, or lack of function of testes)
- Klinefelter’s syndrome
- 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
- Multiple endocrine neoplasia (MEN) I
- Ovarian cysts
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
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.
by Sharon M. Smith, M.D.
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.