The Role of Leutinizing Hormone
Luteinizing hormone, along with follicle-stimulating hormone, are types of hormones called menotropins. These two hormones are responsible for regulating the menstrual cycle and the various events that occur during the cycle.
Follicle-stimulating hormone promotes the growth of the ovarian follicle, a structure within which is contained a developing egg and associated cells.
In the meantime, estrogen production increases in the follicle, causing the endometrium of the uterus to thicken just prior to ovulation. Luteinizing hormone helps promote estrogen production.
The primary function of luteinizing hormone is to trigger ovulation. Just before ovulation, blood levels of the hormone increase sharply, to trigger this event.
Luteinizing hormone plays a role in male fertility too. In men, the hormone stimulates the production of testosterone in the testicles. Levels of this hormone remain fairly constant in men once puberty has passed.
In children, luteinizing hormone levels are at very low levels until the pre-puberty stage.
The Leutinizing Hormone Blood Test
The luteinizing hormone blood test is ordered to check pituitary gland function, as this gland produces the hormone. There are several reasons why a doctor might order this test:
- For a woman who is having difficulty conceiving
- A woman who has heavy or irregular periods
- Someone of either sex with symptoms of an ovarian or testicular disease
- A child of either sex with symptoms of delayed or early sexual maturation
Certain drugs can interfere with luteinizing hormone test results. These include oral birth control, the depo provera birth control injection, hormone replacement therapy, and supplemental testosterone.
To perform the luteinizing hormone blood test the health care provider first cleans the inside of the elbow with an antiseptic. Next he or she wraps an elastic band around the upper arm to make the vein fill with blood. A needle is then inserted into the vein, the elastic is removed, and blood is drawn. Once enough blood has been drawn the needle is removed and the injection site is covered.
The injection typically causes only a mild stinging sensation; some people might feel moderate pain.
Understanding Luteinizing Hormone Test Results
This blood test is often ordered with other tests such as those for follicle-stimulating hormone, testosterone, estrogen, and progesterone. These tests are part of the diagnostic process for infertility causes in both men and women.
Understanding luteinizing hormone test results first requires knowing the normal baseline values of this hormone. In an adult woman, the normal level of luteinizing hormone is 5 to 25 IU per liter of blood. In an adult man, the normal level is 2 to 18 IU per liter of blood.
If levels of luteinizing hormone are higher than normal, there are several diagnostic possibilities:
- Hypogonadism: little or no sex hormone is being produced by the ovaries or testicles
- Klinefelter syndrome: A genetic disorder characterized by low testosterone production in men
- Polycystic ovary disease: hormonal imbalance which causes irregular menstruation, infertility, and the development of ovarian cysts
- Early onset of puberty
If levels of luteinizing hormone are lower than normal the primary cause is generally a dysfunction of the pituitary gland.
Lab Tests Online: Luteinizing Hormone
National Institute of Health Medline Plus: LH Blood Test