Testosterone Bioavailable Test

Testosterone testing is used to diagnose several conditions in men, women, girls, and boys. Testosterone is the main sex hormone in men, produced mainly by the testicles, and is responsible for male physical characteristics. Although it is considered to be a 'male' sex hormone, it is present in the blood of both males and females. About two-thirds of testosterone circulates in the blood bound to sex hormone-binding globulin (SHBG) and slightly less than one-third bound to albumin. A small percent (less than 4%) circulates as free testosterone. Free testosterone plus the testosterone bound to albumin is the bioavailable testosterone, which can act on target tissues. In many cases, the total testosterone test provides 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.

It is recommended that you should either wear a sleeveless or a short-sleeved shirt to make it easier for you and the technician who will be drawing the blood. Wearing a shirt with full- sleeves that can easily be rolled-up is also fine. No special preparation is needed before having this test. Many medicines may change the results of this test. Drugs such as anticonvulsants, barbiturates, and clomiphene can cause testosterone levels to rise. Women taking estrogen therapy may have increased total testosterone levels. Be sure to tell your doctor about all the nonprescription and prescription medicines you take.

Males: Decreased testosterone levels indicate partial or complete hypogonadism. Serum testosterone levels are usually below the reference range. The cause is either primary or secondary/tertiary (pituitary/hypothalamic) testicular failure.

Females: Decreased testosterone levels may be observed in primary or secondary ovarian failure, analogous to the situation in men, alongside the more prominent changes in female hormone levels. Most women with oophorectomy have a significant decrease in testosterone levels. Increased testosterone levels can indicate: PCOS, ovarian or adrenal gland tumor or congenital adrenal hyperplasia

A band is wrapped around the arm, 3-4 inches above the collection site (superficial vein that lies within the elbow pit) A 70% alcohol pad is used to clean the skin A needle is then kept in line with and injected into a vein that can be seen from the skin The blood is dragged out from the needle by a nozzle, saved in a vessel and sealed with your name The sample is then taken to a lab for examination