RESUMEN
Two unrelated boys (C.C. 13 years; J.W. 18 years) presenting with early puberty and episodes of aggressive behaviour were found to have hypernatraemia and hypodipsia. Plasma vasopressin (AVP) levels were inappropriately low in relation to plasma osmolality, but the patients did not have diabetes insipidus since 24 h urinary volumes were less than 1 litre and the maximal urinary osmolality was 1232 in C.C. and 950 in J.W. Plasma renin activity was elevated (greater than 2000 mg AI/1/h) although aldosterone concentrations were normal. Excretion of a water load (20 ml/kg) was delayed, but plasma renin and aldosterone fell with increased naturesis. An infusion of 0.85 mol/l saline produced a rise in AVP in C.C. but not in J.W. Insulin and hypotension resulted in the release of AVP in both boys suggesting a selective defect of osmoreceptor function. Hyperprolactinaemia and an exaggerated PRL response to TRH were also noted but no intracranial lesion was demonstrable on CT scan. These boys appear to have a hypothalamic syndrome with early puberty, hyperprolactinaemia, hypodipsia and osmoreceptor dysfunction which may be associated with aggressive behaviour.