Hypothyroidism is commonly thought to cause decreased gastric emptying and secretion, but these may be related to associated autoimmune disease or chronic changes. Therefore, we measured gastric emptying and secretion in 11 healthy controls and in nine patients (19-54 years old; five females and 4 males) rendered athyreotic by surgery and/or 131I for thyroid cancer. Replacement T4 was stopped 47-65 days and subsequent replacement T3 was stopped 33-40 days before the study. All patients were symptomatic with complaints including weight gain, lethargy, and constipation. Deep tendon reflexes had delayed relaxation phase. Serum cholesterol and creatine phosphokinase levels were elevated. Thyroid hormone levels were markedly decreased (means +/- SE; T4: 0.7 +/- 0.3 micrograms/dl; free T4: 0.2 +/- 0.1 ng/dl; T3: 28 +/- 6 ng/dl) and TSH was markedly increased (88 +/- 16 microU/ml). Gastric fractional emptying rate (%/min) and hydrogen ion (H+) output (meq/hr) were determined before and following two sequential stimulations: a 250-ml water load and an intravenous infusion of pentagastrin (6 micrograms/kg/hr). There were no significant differences between controls and athyreotic patients. Our data demonstrated that short-term, profound, thyroid hormone deficiency does not modify gastric emptying or acid output.