Evidence for normal antidiuretic responses to endogenous and exogenous arginine vasopressin in patients with guanine nucleotide-binding stimulatory protein-deficient pseudohypoparathyroidism

Abstract

In six patients with pseudohypoparathyroidism (PHP) who were deficient in guanine nucleotide-binding stimulatory protein (Ns) activity, the response to endogenous arginine vasopressin (AVP) was tested during water deprivation. Hourly plasma osmolality (Posm), urinary osmolality (Uosm), and urinary AVP (UAVP) values were compared to those in normal subjects. The Uosm vs. Posm and the UAVP vs. Uosm relationships of the patients were all within the normal range. Four patients with Ns-deficient PHP were subjected to maintained water loads and infused with AVP at three different rates for 1 h each to assess their responses to exogenous AVP. Urinary volume and osmolality values from the final 30 min of each infusion rate were measured. All volume values except 1 were within 1.6 SD of normal, and all osmolality values except 1 were within 1.1 SD of normal. In conclusion, these studies indicate that these six patients with Ns-deficient PHP are not resistant to the antidiuretic (cAMP-mediated) action of endogenous or exogenous AVP, in contrast to the previously documented resistance of patients with Ns-deficient PHP to the actions of PTH, TSH, glucagon, and gonadotropins.