Testing for the hormone testosterone is done with a simple blood sample to determine the level of androgen in the bloodstream. While testosterone is referred to as the “male” hormone, affecting physical strength, hair growth and sexual desire in men, it is also produced by females, and plays a role in reproductive health and sexual arousal as well. Because testosterone levels are at their highest in the morning, it is common for blood to be drawn between 7am. and 10am. Some physicians might also request blood draws at intervals throughout the day to monitor fluctuating hormone levels. Certain medications such as, steroids, anticonvulsants, barbiturates, clomiphene, androgen therapy, and estrogen therapy can affect test results, so it is important to notify the physician of any prescriptions or over-the-counter medications you’re taking, before testing.
Why Test Is Used
The doctor may order testosterone testing for either gender, if he or she suspects that hormone levels are too low or too high in an individual. In males it is common to test for early or delayed puberty. Low levels of testosterone can be the cause of a condition known as “hypogonadism” as well. Symptoms include growth of breast tissue, decreased body hair, muscle mass, and sex drive, as well as erectile dysfunction. Too much testosterone can also be the result of testicular or adrenal tumors. In females, high levels of testosterone may be detected if menstrual periods are irregular or male characteristics, such as facial hair or a deepening voice are present. This could also indicate polycystic ovarian syndrome, ovarian tumors, or an adrenal tumor.
How does it work?
In males, the testicles produce 95% of testosterone, while 5% is made in the adrenal glands just above the kidneys. Most testosterone binds to one of two proteins, albumin, or sex hormone binding globulin (SHBG). The rest is referred to as “free testosterone”. Initial testing examines total testosterone, which looks at all three parts of testosterone. In females, testosterone is produced in the ovaries, adrenal gland, and peripheral tissues. Blood drawn from a vein in the arm is required for testing in both males and females. This will be sent to a lab for evaluation.
Results for testosterone testing are provided in nanograms per deciliter (ng/dL). Total testosterone levels within normal range are as follows:
280 to 1,100 ng/dL for men
15 to 70 ng/dL for women
A physician may order more specific testing if results indicate, either too much or too little testosterone in the bloodstream.