17-OH progesterone
What it measures, and what changes the number.
17-OH progesterone (17-hydroxyprogesterone) is a steroid produced by the adrenal glands and the ovaries or testes. It is an intermediate on the pathway that leads to cortisol and to androgens, and the test measures how much of it is present in blood.
It is commonly read together with cortisol, ACTH, androstenedione and progesterone, since these hormones share the same production pathway and their balance helps show how adrenal steroid synthesis is working. It is also part of newborn screening programs.
Levels follow a daily rhythm and tend to be measured from a morning sample. In women the result varies across the menstrual cycle, so labs often ask for a draw in a particular phase. Immunoassays and mass spectrometry methods can give different results, so comparisons are easiest within one lab. Reports may show it as 17-HYDROXYPROGESTERONE, 17-OHP or 17-OH progesterone.
Often read alongside: Cortisol, ACTH, Androstenedione, Progesterone, 17-OH pregnenolone