AVPR1B and Cushing syndrome: On the contrary, knock-out mice lacking the V1bR have a phenotype of low levels of glucose in plasma and better insulin sensitivity, as well as low levels of ACTH and corticosterone, compared to wild type mice (21, 22), suggesting that overstimulation and/or enhanced endogenous activity of V1bR may result in a mild Cushing's syndrome-like phenotype.