Biology and Detection of Pregnanes During Late Gestation in the Mare

This thesis investigated the metabolism and detection of pregnanes during late gestation in mares. It was found that progesterone levels declined significantly, being metabolized into various pregnanes, with 5α-dihydroprogesterone and allopregnanolone identified as bioactive. The study evaluated the impact of the 5α-reductase inhibitor, dutasteride, on pregnane metabolism and pregnancy outcomes, finding significant alterations in metabolism without affecting pregnancy. The research highlighted the limitations of immunoassays due to cross-reactivity and demonstrated that liquid chromatography tandem mass spectrometry (LC-MS/MS) provided more accurate differentiation of pregnanes, showing significant differences in assay results and better correlation with actual progesterone concentrations. This work underscored the complexity of pregnane metabolism and the necessity of LC-MS/MS for precise detection.