Total Testosterone: What Your Result Reflects

Testosterone is a sex hormone that plays a key role in supporting bone health, density and strength as well as libido and sexual function. Testosterone is primarily produced by the testes in males and, to a lesser extent, by the ovaries in females. 98% of testosterone is found bound to carrier proteins (sex-hormone binding globulin (SHBG) and to a lesser degree albumin). Between 1-3% is free, unbound testosterone. Total testosterone measures the testosterone that is biologically active (bound to albumin, but not SHBG) along with that which is inactive.

Testosterone plays a key role in the development and maintenance of male secondary sexual characteristics, including muscle mass, body hair, and a deep voice. It also influences libido and sexual function in both men and women. Additionally, testosterone supports bone health, contributing to bone density and strength. Testosterone is essential for energy, mood, and cognitive function. It has a significant impact on muscle and overall body composition. Low testosterone levels can lead to symptoms like fatigue, reduced muscle mass, mood changes, and sexual dysfunction, while excessively high levels can result in adverse health effects, such as cardiovascular issues. Low testosterone levels in men, known as hypogonadism, can lead to a range of symptoms and may require treatment. In women, imbalances can occur due to polycystic ovary syndrome (PCOS) or other hormonal disorders.

The definition of normal range varies considerably between different guidelines. This is largely due to existing studies extrapolating normal adult ranges from older populations. A 2018 study compiled >1400 adults between the ages of 20-44 to get data in this younger population. The American Urological association considers an optimal range above 33rd percentile i.e. >374 ng/dl (13 nmol/L), this figure can continue for adults >44 years and this is the range adopted by Nia.