Testosterone Free

Testosterone free measures the levels of free testosterone present in the blood. 

Testosterone is a sex hormone which is mainly found in men. It can also be found in women but in small amounts. Testosterone helps in the development of male physical characteristics. 

In men, testosterone is produced by the Leydig cells present in the testicles. It is also produced by the adrenal glands present in both males and females. In females, small amounts of testosterone are produced by the ovaries. 

The function of testosterone is to develop secondary sex characteristics which include enlargement of the penis, body hair growth, development of muscle, and deepening of the voice. During puberty, it is produced in large amounts in males. In adult males, its function is to regulate the sex drive and to maintain muscle mass. In adult females, the testosterone gets converted to estradiol, which is the main sex hormone in females.

The testosterone hormone production is regulated by luteinizing hormone (LH), which is produced by the pituitary gland. As the levels of testosterone rise, the production of LH decreases which in turn slows down the production of testosterone. This is due to the negative feedback system, in which one entity controls the production of others. Similarly, when the levels of testosterone fall, it leads to an increase in production of LH which stimulates testosterone production.

The levels of testosterone are highest in the early morning and lowest in the evening. With exercise, the levels of testosterone increase and with age the levels decrease. 

In the blood, about two-thirds of testosterone hormone is bound to sex-hormone-binding globulin (SHBG) and about one-third is bound to albumin. A small amount is present as free testosterone.