Hormone Testing at Access Medical Laboratories

HORMONE INFORMATION - LH

What is it?

The LH test measures the amount of luteinizing hormone (LH). LH is a protein hormone released by the anterior pituitary gland. In women, an increase in LH levels at mid-cycle causes ovulation. In men, LH stimulates production of testosterone. In both males and females, LH is essential for reproduction. In females, at the time of menstruation, FSH initiates follicular growth, specifically affecting granulosa cells.

With the rise in estrogens, LH receptors are also expressed on the maturing follicle that produces an increasing amount of estradiol. Eventually at the time of the maturation of the follicle, the estrogen rise leads via the hypothalamic interface to the "positive feed-back" effect, a release of LH over a 24-48 hour period. This 'LH surge' triggers ovulation thereby not only releasing the egg, but also initiating the conversion of the residual follicle into a corpus luteum that, in turn, produces progesterone to prepare the endometrium for a possible implantation. LH is necessary to maintain luteal function for the first two weeks.

In case of a pregnancy luteal function will be further maintained by the action of hCG (a hormone very similar to LH) from the newly established pregnancy. LH supports the cells in the ovary that provide androgens and hormonal precursors for estradiol production. In the male, LH acts upon the Leydig cells of the testis and is responsible for the production of testosterone, an androgen that exerts both endocrine activity and intratesticular activity such as spermatogenesis.

The release of LH at the pituitary gland is controlled by pulses of gonadotropin-releasing hormone (GnRH) from the hypothalamus. Those pulses, in turn, are subject to the estrogen feedback from the gonads.

Alternative Names

• ICSH; Luteinizing hormone

Why the Test is Performed

Your doctor may order this test if you are having trouble getting pregnant or have signs of a disorder associated with abnormal levels of LH.

Normal Results

• Adult male: 7 to 24 international units per liter (IU/L)
• Adult female: 5 to 20 IU/L (levels peak around the middle of the menstrual cycle)

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

Greater-than-normal levels of LH may indicate:

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

RESOURCES:

1. lutropin at eMedicine Dictionary

2. Physiology at MCG 5/5ch9/s5ch9_5

3. Physiology at MCG 5/5ch8/s5ch8_5

4. Gonadotropins: Luteinizing and Follicle Stimulating Hormones at colostate.edu