Identification of endogenous 19-nortestosterone in pregnant ewes by gas chromatography-mass spectrometry.

Considered as a xenobiotic for many years, 19-nortestosterone has been extensively studied. Analyses developed to control the illegal use of this steroid in meat-producing animals led researchers to demonstrate the endogenous presence of 19-nortestosterone in several species. In this paper, the natural occurrence of 19-nortestosterone in its alpha form (epinandrolone) in the urine of pregnant sheep was demonstrated using gas chromatography-mass spectrometry. This reference method allowed 17 alpha-nandrolone to be detected and identified, and the absence of the beta epimer in the urine of pregnant sheep to be demonstrated. 17 alpha-Nandrolone was accurately determined at different stages of pregnancy. The analyses showed that epinandrolone, which was not detectable in the urine of non-pregnant sheep, was excreted in small amounts (leading to a < 0.5 ppb concentration) during the first 4 months of pregnancy. 17 alpha-Nandrolone concentrations then increased during the last month until parturition. The origin of this molecule was not determined.