The steroid hormone 17-OH progesterone belongs to the gestagens. It is produced in the adrenal cortex and ovaries. 17-OH progesterone is formed by hydroxylation of progesterone and is a precursor of glucocorticoids, mineralocorticoids and androgens. During biosynthesis of the glucocorticoid cortisol the enzyme 21-hydroxylase converts 17-OH progesterone to 11-desoxycortisol in the adrenal cortex. Therefore, 17-OH-progesterone is considered an indirect parameter for 21-hydroxylase enzyme activity of the adrenal cortex.

With congenital adrenal syndrome, a group of metabolic disorders, the hormone synthesis in the adrenal cortex is disturbed. Deficiency in 21-hydroxylase causes more than 90% of cases of congenital adrenal hyperplasia (CAH). As a consequence, 17-OH progesterone accumulates and causes an excess of androgens, which, in women, is associated with virilisation and hyperandrogenism. This results in a deficiency in glucocorticoids and mineralocorticoids.