SHBG
The Test
How is it used?
SHBG and testosterone levels may be ordered on an adult male to help determine the cause of infertility, a decreased sex drive, and erectile dysfunction, especially when total testosterone results are inconsistent with clinical signs.
In women, small amounts of testosterone are produced by the ovaries and adrenal glands. Even slight increases in testosterone production can disrupt the balance of hormones and cause symptoms such as amenorrhoea, infertility, acne, and hirsutism. These symptoms and others are often seen with polycystic ovarian syndrome, a condition characterised by an excess production of androgens. SHBG and testosterone testing may be useful in helping to detect and evaluate excess testosterone production and/or decreased SHBG concentrations.
For both sexes, a free testosterone, albumin level, and one or more other hormones, such as prolactin, oestradiol, and LH (luteinising hormone) may also be performed to help evaluate a patient’s existing balance of hormones.
Sometimes, a total testosterone and SHBG are ordered to help evaluate free androgens by calculating the Free Androgen Index (FAI). This equation gives doctors an idea of the quantity of testosterone that is not bound to SHBG and is calculated as follows: FAI=total testosterone / SHBG x 100.
When is it requested?
What does the test result mean?
Is there anything else I should know?
Bioavailable testosterone is becoming an increasingly important concept to both doctors and researchers. It may be measured by removing the SHBG-bound testosterone from the collected blood sample and then analyzing what’s left. An estimate can also be calculated using the Free Androgen Index (see above).
Although SHBG is not usually ordered to diagnose or monitor these conditions, increases in SHBG are seen with liver disease, hyperthyroidism, anorexia, and oestrogen use (replacement and oral contraceptive). Decreases in SHBG are seen with obesity, hypothyroidism, androgen use, and Cushing’s disease.
