The menstrual cycle is governed by the interaction of hormones that allow an egg-containing follicle to grow. Follicle-stimulating hormone, or FSH, plays an important role in the recruitment and development of eggs each month. Abnormal FSH levels more often are elevated, but may be suppressed in some cases. FSH rises normally in menopause.
Definition
FSH is a hormone produced in the pituitary gland. The normal level of FSH in the blood at the beginning of the menstrual cycle in women of childbearing age is 5 to 11milli-International Units per Liter, or mIU/L. Levels over 11mIU/L indicate decreased ovarian reserve, or a drop in the number of follicle-containing eggs still found in the ovaries. Levels over 20 mIU indicate a very low reserve, and levels over 40 mIU/L indicate menopause, Advanced Fertility of Chicago explains. FSH levels vary during the menstrual cycle, so levels must be tested on day 2 or 3 of the cycle to accurately assess ovarian reserve.
Significance
When estrogen levels drop at the start of a new menstrual cycle, FSH rises slightly to stimulate the ovaries to produce more estrogen and to develop more follicles. FSH levels surge slightly around the time of ovulation. Abnormally high levels of FSH result from a decrease in the number of follicles left in the ovary. The normal amount of FSH doesn't stimulate follicle growth, so the pituitary increases the amount released, trying to force the ovaries to produce estrogen and develop follicles.
Causes
In women under age 40, an elevated FSH indicates premature ovarian failure, or POF, according to Advanced Fertility of Chicago. Over age 40, a high FSH indicates menopause. Autoimmune disease, chemotherapy or radiation treatments and thyroid or adrenal disease can also cause elevated FSH levels, Lab Tests Online says.
Very low levels of FSH may indicate a problem with the pituitary gland or hypothalamus, and have been implicated with an increased risk of ovarian cancer, states Lab Tests Online.
Effects
FSH levels rise when ovarian reserve decreases. For women trying to get pregnant, a high FSH means that she may not ovulate very often, or at all. A high FSH makes it difficult to get pregnant without the help of a fertility specialist, and if FSH levels are over 20 mIU/L, the chances may be exceedingly low.
Treatment
A woman with high FSH who wants to get pregnant may be prescribed medications such as estrogen or synthetic estrogen to try to decrease FSH. Estrogen medications fool the body into thinking it is producing estrogen. Since the pituitary now believes there's an adequate amount of estrogen in the body, it decreases production of FSH, so levels drop. This allows the ovary to ripen and mature an egg-containing follicle if there are any left in the ovary, according to Jerome Check, M.D., in a 2000 article published in "Human Reproduction."
