Influence of glucocorticoid therapy, Cushing's syndrome and hypothyroidism on the reproductive cycle and AMH levels in the bitch.

Glucocorticoids can inhibit the pulsatile secretion of Gonadotropin-releasing-hormone (GnRH). Therefore, if the body's own cortisol is permanently elevated, as is the case in Cushing's syndrome or exogenous treatment with glucocorticoids, gonadotropin secretion can be weakened. Additionally, women's menstrual cycle and fertility can be affected due to hypothyroidism. Anti-Müllerian hormone (AMH) produced by granulosa cells is described as a fertility marker. The aim of this study was to investigate the effects of Cushing's syndrome or exogenous glucocorticoids and hypothyroidism on the reproductive cycle and AMH-levels in bitches. Gynaecological examinations and AMH measurements were performed in 42 dogs of different breeds. Twenty-eight received cortisone (prednisolone), ranged from 0.1 to 2.1 mg/kg orally once per day, 6 had Cushing's syndrome and 8 hypothyroidisms. Twenty-eight healthy female dogs served as a control group. Seventeen bitches with cortisone treatment showed prolonged anestrus, 8 of them returned to heat after discontinuation or reduction of the dosage. Two bitches experienced delayed onset of puberty. Two bitches with Cushing's syndrome showed prolonged anestrus, too, but none with hypothyroidism exhibited cycle alterations. The AMH values between the different groups did not differ (p = 0.14). The AMH levels of all 21 bitches with changes in their estrous cycle did not differ from those of the bitches without changes (p = 0.47). Cortisone treatment can suppress estrus in bitches. Cushing's syndrome may lead to prolonged anestrus, while hypothyroidism seems to have no effect on the estrous cycle, but a larger experimental group is required to assess these effects. Bitches with cycle alterations showed no change of AMH level.