Steatorrhea in Thyrotoxicosis

Detailed studies of intestinal absorptive function were done in 10 untreated hyperthyroid patients to elucidate the mechanisms causing thyrotoxic steatorrhea. Serum calcium, serum iron, prothrombin time, jejunal biopsies, cultures of intraluminal contents, and secretin tests were normal in all patients. Vitamin B12 and D-xylose absorption were normal in 9 of 10 patients. All patients showed rapid intestinal transit. Lactose intolerance, initially present in two patients, disappeared after 131I therapy for thyrotoxicosis. On an ad libitum diet there was gross steatorrhea in six patients. The coefficient of fat absorption was only slightly abnormal in five, showing excessive dietary fat ingestion in these patients (mean fat intake, 248 g/24 hr). In two patients propranolol significantly prolonged intestinal transit time and reduced steatorrhea by 48% and 50%, respectively. The data suggest that steatorrhea in hyperthyroidism is probably caused by the combined effects of excessive dietary fat intake and intestinal hypermotility.