Vasopressin and thirst in patients with posterior pituitary ectopia and hypopituitarism

OBJECTIVE Partial diabetes insipidus has been documented in patients with c ongenital hypopituitarism and posterior pituitary ectopia, some cases being clinically silent except for enuresis, The objective of our study was to e valuate vasopressin (AVP) secretion and thirst appreciation in hypopituitar y patients with posterior pituitary ectopia. PATIENTS Twelve males and three females, aged between 13 and 38 years (medi an 19 years). Eleven had multiple pituitary deficiencies, adequately replac ed at the time of the study, and four were only growth hormone deficient, N one of the patients suffered from polyuria, polydipsia or nocturnal enuresi s, We tested the patients with a 5% NaCl infusion. Five patients with abnor mal vasopressin production were also tested with nitroprusside, which affec ts baroceptor vasopressin secretion. RESULTS We found that only two out of 12 patients had normal AVP secretion. Thirst assessment showed severe hypodipsia in one patient, hyperdipsia in three out of 15 and more subtle abnormalities in two out of 15 patients. Co ncordance was found between osmotically and baroceptor-stimulated vasopress in. CONCLUSIONS Patients with posterior pituitary ectopia showed a high prevale nce of subclinical subnormal vasopressin response to the osmolar stimulus a nd moreover an impairment of thirst appreciation. Our data on nonsomoticall y stimulated AVP release suggest the existence of a damage in the hypothala mic vasopressin secreting centres.