Testosterone is the primary male androgen; its synthesis is performed almost exclusively in testicular Leydig cells. Testosterone secretion is controlled by the pituitary luteinizing hormone LH produced by the pituitary and is subject to a negative feedback mediated by the hypothalamus and pituitary. The majority of circulating testosterone is bound to sex hormone binding globulin (SHBG = sex hormone binding globulin).
Testosterone is involved both in the development of male sexual characteristics and in maintaining the function of the prostate and seminal vesicles.
Women produce much smaller amounts of testosterone and dihydrotestosterone. The ovaries and adrenal glands have little contribution in terms of androgen synthesis, mostly in the amount of testosterone produced in women resulting from peripheral conversion of other steroids. In physiological concentrations of androgens have specific effects in women, but if this growth occurring hormone (hiper- androgenemia) appear manifestations of hirsutism (excessive hair growth in male distribution) or even virilization (hirsutism added with muscle growth , androgenic alopecia, acne, deepening of the voice, clitoral enlargement).
Recommendations for determination of testosterone
a) clinical suspicion of androgen deficiency (primary hypogonadism, hypopituitarism, Klinefelter syndrome, Down syndrome, delayed puberty, sexual impotence, infertility, estrogen therapy, cirrhosis);
b) clinical suspicion of androgen excess: adrenocortical tumors, precocious puberty.
In women: hirsutism, anovulation, amenorrhea or virilization (possible causes: polycystic ovarian syndrome, virilizing ovarian tumors, adrenal tumors or adrenogenital syndromes).
Reference values - dependent on age and sex.
Conversion factors: nmol / L x 0.288 = ng / mL; ng / ml x 3.47 = nmol / L; ng / mL x 100 = ng / dL.
Breakpoints -> 5 nmol / L in women – suspicion of tumor process.