Influence of thyroid states on stress gastric ulcer formation.

Thyroid hormones exert a critical developmental and regulatory role on the morphology and biochemistry of gastrointestinal mucosal cells. However, the relationship between thyroid function and stress gastric lesion formation remains undetermined. This study was designed to test the hypothesis that thyroid states may affect the acute development of gastric lesions induced by cold-restraint stress. Normal (euthyroid), hyperthyroid (200 micrograms of T4 i.p. x 7 days) and hypothyroid (thyroidectomized) rats were used. Gastric lesion incidence and severity was significantly (p less than 0.05) increased in hypothyroid rats, whereas in contrast hyperthyroid rats developed significantly less gastric lesions. As anticipated, plasma levels of thyroxin (T4) were significantly (p less than 0.01) elevated in hyperthyroid rats, and undetectable in hypothyroid rats. Acute pretreatment with i.p. cimetidine (100 mg/Kg), but not T4 (200 micrograms/Kg) 1 h prior to stress completely prevented gastric lesions formation in hypothyroid rats. Finally, binding of 3H-dihydroalprenolol to beta-adrenergic receptors on brain membranes prepared from frontal cortex was reduced by 20% in hypothyroid rats after 3 h of stress. These and other data contained herein suggest that thyroid hormones contribute to modulate the responsiveness of the gastric mucosa to stress. The increased rate of ulcerogenesis observed in hypothyroid rats appears to be mediated by gastric acid secretion. The central mechanism of this response may involve decreased brain nonadrenergic receptor function.