17α-hydroxyprogesterone (17-OH progesterone or 17OHP) is a steroid hormone produced in the adrenal gland and gonads. (1,2,3) It is synthesized from progesterone, and it serves primarily as a precursor compound that is converted into cortisol in the adrenal gland, or into androgenic and estrogenic steroid hormones in the gonads. (3,4) 17-OHP is routinely used for the diagnostic assessment of 21-hydroxylase deficiency, which is linked to congenital adrenal hyperplasia, impaired aldosterone synthesis, and fatal salt-wasting. (5,6,7,8,9)  17-OHP exhibits a diurnal rhythm with higher values in the morning and decreasing over the day to a nadir in the evening. (10,11) 17-OHP enters saliva from blood via intracellular mechanisms, and there is excellent correlation between saliva and serum values. (12)