Progesterone itself is not readily found in the urine. Instead, this test measures pregnanediol (a progesterone metabolite). Pregnanediol is well-established in research literature as a reliable marker for progesterone levels.
The primary role of progesterone is to balance the strong effects of estrogen. Progesterone metabolites are measured and reflect progesterone levels well because very little progesterone is found in urine, so b-Pregnanediol is typically used as a surrogate marker because it is the most abundant metabolite, but we also test the corresponding a-pregnanediol. The average of the two metabolites is reported for progesterone. If levels are in the lower part of the reference range compared to estrogen levels, symptoms of too much estrogen may occur.
Pregnanediol
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