TESTOSTERONE, FREE, BIOAVAILABLE AND TOTAL, MALES (ADULT) IMMUNOASSAY

Testosterone, Total, Males (Adult), Immunoassay; Albumin; Sex Hormone Binding Globulin (SHBG); Testosterone, Free and Bioavailable (calculated)

A testosterone test measures the blood level of the male sex hormone testosterone. Testosterone, which plays an important role in sexual development, is produced mainly by the testes in boys and in much smaller amounts by the ovaries in girls. Testosterone is also produced by the adrenal glands in both girls and boys.

In young boys, testosterone levels are normally low. As puberty approaches — usually between the ages of 10 and 14 — the pituitary gland (a pea-sized gland near the base of the brain) secretes two hormones (luteinizing hormone, or LH; and follicle-stimulating hormone, or FSH) that work together to stimulate the testes to make testosterone.

Increased testosterone production is what causes boys to develop deeper voices, bigger muscles, and body and facial hair. It also helps the testes produce sperm, and it plays a role in speeding a boy's growth in height during puberty. Testosterone is also important for bone health.

Two separate assessments may be performed as part of a testosterone test:

• Total testosterone; which measures the entire amount of testosterone in the body, including both the amount bound to proteins that help transport the hormone through the bloodstream .
• Free testosterone; which measures only the testosterone that's not attached to proteins