Testosterone, Total, Serum/Plasma

The hormone testosterone is derived from cholesterol. The largest amounts of testosterone are produced by the testes in men. It is also synthesized in far smaller quantities in women by the thecal cells of the ovaries, by the placenta, as well as by the zona reticularis of the adrenal cortex in both sexes. In the testes, testosterone is produced by the Leydig cells. The male generative glands also contain Sertoli cells which require testosterone for spermatogenesis. Like most hormones, testosterone is supplied to target tissues in the blood where much of it is transported bound to a specific plasma protein, sex hormone binding globulin (SHBG). The effects of testosterone can be classified as virilizing and anabolic, although the distinction is somewhat artificial, as many of the effects can be considered both. Anabolic effects include growth of muscle mass and strength, increased bone density and strength, and stimulation of linear growth and bone maturation. Virilizing effects include maturation of the sex organs, particularly the penis and the formation of the scrotum in unborn children and after birth (usually at puberty) a deepening of the voice, growth of the beard and axillary hair.

Serum concentrations of testosterone in both sexes during the first week of life average about 0.25 ng/mL. Conditions such as hypogonadism, hypopituitarism, orchiectomy, oestrogen therapy, and some cases of Klinefelter’s syndrome are associated with decreased levels of testosterone. Levels increase from puberty to adult values and are related to pubertal stage rather than chronological age. In addition, total testosterone measurements have traditionally been used to help in the diagnosis of the underlying cause of hirsutism.

1 ml Serum 1 ml Li-Heparin or K2, K3-EDTA Plasma Stability: 1 Week at 2-8 °C 6 Months at -20 °C

Freeze only once.

Male (7-19 Years): < 0.025-8.82 ng/mL < 0.087-30.6 nmol/L Male (20-49 Years): 2.49-8.36 ng/mL 8.64-29.0 nmol/L Male ( ≥ 50 Years): 1.93-7.40 ng/mL 6.70-25.7 nmol/L Female (8-19 Years): < 0.025-0.383 ng/mL < 0.087-1.33 nmol/L Female (20-49 Years): 0.084-0.481 ng/mL 0.291-1.67 nmol/L Female ( ≥ 50 Years): 0.029-0.408 ng/mL 0.101-1.42 nmol/L