Androgens are a group of steroids which cause masculinisations of the genital tract and the development and maintenance of male secondary sexual characteristics. They also contribute to muscle bulk, bone mass, libido and sexual performance in men. Testosterone is the major androgen secreted by the Leydig cells of the testes, and its production increases during puberty. Women produce about 5% to 10% as much testosterone as men. Testosterone directly effects some aspects of secondary sexual characteristics such as deepening of voice, increase of muscle mass and libido and also has some indirect effects in tissue with high 5alpha-reductase activity, where it serves as a prohormone to formation of dihydrotestosterone.
Testosterone may be requested, together with measurement of FSH and LH, in males for invesigation of sexual dysfunction or infertility.
In the female, testosterone is secreted by the ovary (60%) and is also derived from the peripheral conversion of androstenedione (40%) which is secreted in equal amounts by the ovary and adrenal. Hence, elevated serum testosterone levels can either be of ovarian or adrenal origin. Testosterone may be requested, together with other endocrine investigations, for the investigation of secondary amenorrhea, infertility or hirsutism/virilization. Due to the normally lower ciculating levels of testosterone in females, this automated method does not have the required sensitivity to measure Female Testosterone levels to the required precision and accuracy. Therefore a seperate LC-MS/MS assay, Female Testosterone, is used in the laboratory for female patients.
Testosterone is measured as part of a steroid profile containing androstenedione and 17-OHP.
Female: <1.9 nmol/L
Male: 7.0-27.0 nmol/L
Female Tanner stage 1: <0.6 nmol/L
Male Tanner stage 1: <0.7 nmol/L