Pregnanediol-3-Glucuronide (5B-pregnane-3a,20a-diol-3a-glucuronide, PDG or P3G) is the major metabolite of progesterone, an endogenous steroid and the most important member of the class of steroid hormones known as progestogens. Progesterone is important in a variety of biological functions such as preparing the endometrium for implantation, maintaining pregnancy, differentiating breast tissue, and promoting normal development of neurons in the brain as a neuro steroid. Low progesterone levels are linked to chronic anovulation which is reported to be associated with female infertility, breast cancer and endometrial cancer.{35256,35090} Levels of PDG in the urine correlate highly to levels of progesterone measured in the serum.{40241,1594} PDG analysis may be used as a non-invasive method to indirectly measure progesterone and therefore might be used as a biomarker for luteal activity, ovarian cancer, and a variety of other biological disorders.{35257,35088,35258}