AVPR2 and nephrogenic diabetes insipidus: A few of gain-of-function mutations, such as R137C, R137L I130N and F229V that cause constitutive activation of receptors, leading to X-linked nephrogenic syndrome of inappropriate antidiuresis (NSIAD)15, 16, while most of AVPR2 gene mutations are loss-of-function that cause X-linked nephrogenic diabetes insipidus (X-linked NDI)7, 17, 18.