Thyroxine in goiter, helicobacter pylori infection, and chronic gastritis

ABSTRACT

Levothyroxine is absorbed between 62% and 72% from the jejunum and ileum. This intestinal absorption is pivotal to its clinical efficacy and is affected by several factors including age, adherence to therapy, dietary habits, absorption kinetics, malabsorption, interference of other drugs, and acid in the stomach. On the other hand Helicobacter pylori [HP] gastritis, corpus atrophic gastritis as well as patients receiving long-term proton pump inhibitors are rather frequent in western countries. We determined whether there is an increased need for thyroxine in patients with euthyroid multinodular goiter [MNG] and impaired secretion of gastric acid. We assessed the dose of thyroxine required to obtain a low level of thyrotropin [TSH, 0.05 to 0.20 mU per liter] in 248 patients with MNG. Of these 248 patients, 53 also had HP-related gastritis and 60 had atrophic gastritis [31 with evidence of HP infection and 29 without]. The reference group comprised 135 patients with MNG and no gastric disorders. In addition, variation in the level of serum TSH was prospectively studied in 11 patients treated with thyroxine before and after HP infection and both before and during treatment with omeprazole in 10 patients treated with thyroxine who had gastroesophageal reflux disease [GERD]. The daily requirement of thyroxine was higher [by 22 - 34%] in patients with HP-related gastritis, atrophic gastritis, or both conditions than in the reference group. In prospective studies, the occurrence of HP infection in the 11 patients treated with thyroxine led to an increase in the level of serum TSH [P = 0.002], an effect that was nearly reversed with HP eradication. In a similar way, omeprazole treatment was associated with an increase in the level of serum TSH in all 10 patients treated with thyroxine, an effect that was reversed by an increase in the thyroxine dose by 37%. Patients with impaired acid secretion require an increased dose of thyroxine, suggesting that normal gastric acid secretion is necessary for effective absorption of oral thyroxine