What is testosterone?

Testosterone is a steroid hormone that plays a key role in the development of the male reproductive system, muscle mass and body hair. Testosterone levels decline with age in males, a process known as andropause, resulting in physiological changes including reduced muscle strength and bone density. Testosterone also has important functions in women contributing to bone health, fertility, menstrual cycle and sex drive.

Not all of the testosterone in the body is available for tissues to utilise. Testosterone binds with sex hormone-binding globulin (SHBG) or albumin, regulating the amount the body can use at any given time. Testosterone that is not bound to SHBG or albumin and is available for the body to use is known as bioavailable testosterone. Symptoms of low testosterone include reduced bone and muscle mass and low sex drive.

Why take the test?

This test measures the amount of testosterone in the blood. In men, it can help to investigate low sex drive, erectile dysfunction, infertility or problems related to the pituitary gland. In women, this test can help to investigate polycystic ovary syndrome (POCS), or tumour of the adrenal gland or ovaries.