Syndrome of inappropriate secretion of antidiuretic hormone (SIADH) and Gerhardt syndrome associated with Shy-Drager syndrome.

This is the first report on a case of syndrome of inappropriate secretion of antidiuretic hormone (SIADH) associated with Gerhardt syndrome (paralysis of bilateral vocal cords). A 67-year-old Japanese man suffering from progressive autonomic failure was diagnosed as having Shy-Drager syndrome (SDS) with hyponatremia due to SIADH and severe sleep apnea caused by a bilateral recurrent nerve palsy. Water load test showed alteration in diuresis which was corrected by phenytoin. Arginine vasopressin secretion was not suppressed by plasma osmolality below 280 mOsm/kgH2O. Impairment of the afferent pathways of baroreceptors, or impairment of the osmoreceptors could be speculated as the etiological factor of the SIADH observed in this case.