17-hydroxyprogesterone (17-OHPROG) is produced mainly in the adrenal cortex, placenta, and, to some extent, in the gonads. The level of 17-hydroxyprogesterone increases when enzymes involved in cortisol synthesis are defective. Measurement of 17-hydroxyprogesterone levels may also be utilized to help in the diagnosis of late-onset CAH in females with hirsutism and irregular menstrual cycles.