Influence of human choriongonadotropin on the concentration of Anti-Muellerian-hormone in cyclic mares

The Anti-Muellerian-Hormone (AMH) is a dimeric glykoprotein of the transforming growth factor superfamily and plays an important role in sexual differentiation during embryo development but also during follicle development. AMH can be used as a biomarker in artificial reproduction technologies, predicting success of superovulation. There is also a relation between AMH and fertility, and AMH correlates well with primordial follicular pool leading to a diagnostic value for the ovarian reserve. The present study investigated the effect of the ovulation inducing agent human choriongonadotropin (hCG) on the concentration of AMH in serum of cyclic mares. Serum concentrations of AMH were evaluated during oestrus immediately before (T-2) and 24 hours following administration of hCG (T-1), at ovulation (T0) and day 7 to 9 post ovulation (T+ 1). The concentration of AMH (ng/ml, median; minimum-maximum) did not differ between mares treated with hCG (T-2: 0.33; 0.16-2.00; T-1: 0.40; 0.17-2.06; T0: 0.42; 0.20-2.07; T+ 1: 0.38; 0.21-1.82) and controls (T-2: 0.48; 0.13-1.47; T-1: 0.59; 0.17-1.48; T0: 0.62; 0.14-1.70; T+ 1: 0.47; 0.17-1.17; p> 0.05). Among single measurements on different days of oestrous cycle, there was no difference in serum AMH (p> 0,05). Administration of hCG to induce ovulation had no influence on the pregnancy rate (control group: 80%; treated group 70%; p> 0.05) and significantly enhanced time of ovulation (control group: 4, 2 to 6; treated group: 2, 2 to 2 days; median, minimum to maximum; p< 0.05). Serum AMH concentration during oestrus and on the day of ovulation did not differ dependent from pregnancy success (pregnant: 0.37; 0.13-1.47; 0.45; 0.17-2.06; 0.61; 0.14-1.70; non-pregnant: 0.67; 0.33-2.00; 0.71; 0.32-2.00; 0.58; 0.34-2.07ng/ml at T-2, T-1 and T0, respectively; p> 0.05). However, in mid dioestrus AMH concentration had the tendency to be higher in non-pregnant mares (pregnant: 0.42; 0.17-1.17; non-pregnant: 0.63; 0.32-1.82ng/ml; at T+ 1; p= 0.08). Further studies are needed to evaluate AMH concentration on defined days during oestrous cycle and early pregnancy to evaluate the prognostic value of AMH concentration for mare fertility.