17-OH pregnenolone
What it measures, and what changes the number.
17-OH pregnenolone (17-hydroxypregnenolone) is a steroid made mainly in the adrenal glands and, to a lesser extent, the ovaries and testes. It sits early in the steroid production chain: the body makes it from pregnenolone and then converts it into 17-OH progesterone or DHEA. The test measures how much of this intermediate is circulating in blood.
It is usually read as part of a panel of adrenal steroids, alongside pregnenolone, 17-OH progesterone, DHEA, DHEA-S and cortisol, because comparing steps in the same pathway shows where production may be slowing or backing up.
Adrenal steroids follow a daily rhythm, so samples are often drawn in the morning, and in women the phase of the menstrual cycle can matter. This is a specialized test, frequently sent to a reference laboratory and often measured by mass spectrometry, and methods can differ between labs. Reports may list it as 17-hydroxypregnenolone or 17 hidroxi Pregnenolona.
Often read alongside: Pregnenolone, 17-OH progesterone, DHEA, DHEA-S, Cortisol