Relationship between corticotropin and vasopressin in endocrine diseases

Vasopressin: The action of vasopressin (AVP) is not limited to regulating w ater excretion but also plays an essential role in regulating the corticotr opic axis during stress. Physiology: Vasopressin is synthesized in the hypothalamus and stored in th e posterior pituitary. It acts on 3 types of receptors (RV). RV1a are vascu lar receptors mediating the vasoconstrictor and glycogenolytic effects of t he hormone. Anterior pituitary RV1b or V3 mediate stimulating effects on th e corticotropic axis. Renal RV2 regulate water and urea excretion. Hypothet ical extrarenal RV2 would be responsible for the vasodilator and procoagula nt effects of the hormone. Modifications in endocrine diseases: Pituitary or adrenal hypocorticism syn dromes include hyponatremia with secondary plasma hypoosmolality and reduce d glomerular filtration due to the direct effect of glucocorticoids and als o the effect of vasopressinism. Certain endogenous hypercorticisms appear t o be related to an overexpression of RV: in ACTH-independent Cushingis synd rome, adrenal overexpression of eutopic RV1a, and in ACTH-dependent Cushing is syndrome, pituitary overexpression of eutopic RV1b or ectopic RV2. in ad dition, inappropirate secretion of antidiuretic hormone is frequent after t ransphenoidal surgery, particularly for corticotropic adenomas. Dynamic tests: The physiological response of ACTH and also AVP to corticotr opin releasing hormone (CRH) in the petrous sinus, the unusual rsponses of certain corticotropic tumors to dDAVP, or certain forms of ACTH-independent hypercortisolism to lysine vasopressin (LVP) suggest excessive or ectopic expression of RV in corticotropic or adrenal cells: tumorgenesis of these c ells could also depend, at least partially on AVP.