Hydroxyprogesterone
It serves as an intermediate in the biosynthesis of hydrocortisone and gonadal steroid hormones. It is derived from progesterone via 17-hydroxylase, a P450c17 enzyme, or from 17-hydroxypregnenolone via 3&#946;-hydroxysteroid dehydrogenase/&#916;5-4 isomerase. 17-Hydroxyprogesterone is a natural progestin and in pregnancy increases in the third trimester primarily due to fetal adrenal production. This hormone is primarily produced in the adrenal glands and to some degree in the gonads, specifically the corpus luteum of the ovary. Normal levels are 3-90 ng/dl in children, and in women, 15-70 ng/dl prior to ovulation, and 35-290 ng/dl during the luteal phase. Measurements of levels of 17-hydroxyprogesterone are useful in the evaluation of patients with suspected congenital adrenal hyperplasia as the typical enzymes that are defective, namely 21-hydroxylase and 11&#946;-hydroxylase, lead to a build-up of 17OHP. In contrast, the rare patient with 17&#945;-hydroxylase deficiency will have very low or undetectable levels of 17OHP. 17OHP levels can also be used to measure contribution of progestational activity of the corpus luteum during pregnancy as progesterone but not 17OHP is also contributed by the placenta.