Estradiol, FSH, SHBG, Testosterone Free and Total

Estradiol (estradiol-17 beta, E2) is part of an estrogen that is a group of steroids that regulate the menstrual cycle and function as the main female sex hormones. Estrogens are responsible for the development of female sex organs and secondary sex characteristics and are tied to the menstrual cycle and pregnancy. They are considered the main sex hormones in women and are present in small quantities in men. Estradiol (E2) is the predominant form of estrogen and is produced primarily in the ovaries with additional amounts produced by the adrenal glands in women and in the testes and adrenal glands in men. Estradiol levels are used in evaluating ovarian function. Estradiol levels are increased in cases of early (precocious) puberty in girls and gynecomastia in men. Its main use has been in the differential diagnosis of amenorrhea – for example, to determine whether the cause is menopause, pregnancy, or a medical problem. In assisted reproductive technology (ART), serial measurements are used to monitor follicle development in the ovary in the days prior to in vitro fertilization. Estradiol is also sometimes used to monitor menopausal hormone replacement therapy.

The sex hormone binding globulin (SHBG) test measures the concentration of SHBG in the blood. SHBG is a protein that is produced by the liver and binds tightly to testosterone, dihydrotestosterone (DHT), and estradiol (an estrogen). In this bound state, it transports them in the blood as an inactive form. The amount of SHBG in circulation is affected by age and sex, by decreased or increased testosterone or estrogen production and can be affected by certain diseases and conditions such as liver disease, hyperthyroidism or hypothyroidism, and obesity. Changes in SHBG levels can affect the amount of testosterone that is available to be used by the body's tissues. A total testosterone test does not distinguish between bound and unbound testosterone but determines the overall quantity of testosterone. If a person's SHBG level is not normal, then the total testosterone may not be an accurate representation of the amount of testosterone that is available to the person's tissues.

In many cases, measurement of total testosterone provides the doctor with adequate information. However, in certain cases, for example when the level of SHBG is abnormal, a test for free or bioavailable testosterone may be performed as it may more accurately reflect the presence of a medical condition.

A testosterone test measures the amount of the male hormone, testosterone, in the blood. Both men and women produce this hormone. In males, the testicles produce most of the testosterone in the body. Levels are most often checked to evaluate signs of low testosterone: In boys -- early or late puberty and in men -- impotence, low level of sexual interest, infertility, thinning of the bones In females, the ovaries produce most of the testosterone and levels are most often checked to evaluate signs of higher testosterone levels, such as: decreased breast size, excess hair growth, increased size of the clitoris. irregular or absent menstrual periods and male-pattern baldness or hair thinning.