EN
The use of exogenous steroids, including gestagens, risks several adverse effects. One of them is cystic endometrial hyperplasia (hyperplasia glandularis cystica). Estrogens stimulate the endometrial development of progesterone receptors. Progesterone and gestagens influence the hyperplasia, proliferation and secretion of endometrial glands, creating the conditions for the emergence of cysts of different sizes with partial leucocytic infiltration. Endometritis-pyometra-complex and mammary tumors are the most common pathologic findings in bitches and queens treated with gestagens. Additionally, hyperglycemia and acromegaly have been observed. These side effects are found to be mainly due to induced GH production in the mammary gland and mediated by IGF-1. The other described adverse effects are adrenocortical suppression, hepatopathy, congenital malformations, prolonged pregnancy, behavioral disorders and local alterations. In some animals in which gestagens were administrated prolactin release increases when gestagen concentration decreases.