Urinary excretion of 5(10)-estrene-3β,17α-diol and estrone by the female horse: Complementary indicators of early pregnancy screened with regard to a putative anabolic doping practice

Rules of horse racing stipulate that pregnant mares may compete under definite conditions of date, because early pregnant status may be misused for the sake of enhancing physical performance by putative anabolic steroid action. Screening for pregnancy is generally performed by plasma equine gonadotrophin (eCG) immunoassay, which covers the period between Days 40 and 120. In common screening for urinary anabolic steroids performed by gas chromatography–mass spectrometry, inclusion of two complementary criteria, i.e. the evaluation of total conjugates of 5(10)-estrene-3β,17α-diol (EED) and estrone (E1), can easily be performed. Although EED and E1 have no anabolic property per se in the horse, assessing these two markers may be helpful in the period comprised between Days 70 and 250, thereby prolonging the detection period behind that of eCG. Peak values of EED and E1 are then attained, so that visual inspection of chromatographic tracings remains in general sufficient as a diagnostic tool. Comparison of EED and E1 during pregnancy and in an estrus cycle indicates a drastic difference in the attained excretion values, attributable to either the placenta or the ovarian follicle. The identity of EED has been proven by GC–MSn in urine and in placental tissue.