Growth Hormone (GH) secretion was studied in a 61-year-old woman with idiopathic orthostatic hypotension (IOH) or Shy-Drager Syndrome. The 24-hour pattern of GH secretion showed multiple daytime peaks and little nighttime activity. The largest daytime peak of 35.0 ng/ml is much greater than the levels observed in seven studies using five age-matched normal women. There were few secretory episodes during sleep in the patient and the control subjects. Paradoxical GH responses occurred during oral glucose tolerance tests, despite high blood glucose. GH was also detected in three studies using TRH. These data suggest that our patient with IOH has abnormal regulation of GH secretion. This is a sign of hypothalamic-pituitary dysfunction in a diffuse neurological disease.