Testosterone is the principal androgen, made mainly in the testes and, in smaller amounts, in the ovaries and adrenal cortex. The usual assay reports total testosterone, meaning both the fraction bound to carrier proteins and the small free fraction together. It speaks for the gonadal axis and, indirectly, for the pituitary signals that drive it.
No readings for this marker yet.
Lowered values in men most often accompany testicular failure, pituitary or hypothalamic suppression, obesity, chronic illness, opioid or glucocorticoid use, and they tend to drift down with age. Raised values in women most often point at polycystic ovary syndrome or an adrenal source of androgen; in men, raised results usually reflect exogenous testosterone. Because carrier protein levels move the total independently of what tissues actually see, a result near either edge is a reason to re-test and take it to a doctor rather than a conclusion.
Secretion follows a daily rhythm with a morning peak, so the sample is normally drawn in the early morning and after fasting; acute illness, poor sleep, and heavy exertion the day before all lower it transiently. Total testosterone is read alongside SHBG, which sets how much is bound, and alongside LH and FSH, which separate a testicular cause from a pituitary one. Estradiol and prolactin are added when the picture suggests aromatisation or a pituitary process.
Reference ranges are general adult values and depend on lab, assay, age and sex. For orientation, not diagnosis — discuss results with your doctor.