Malabsorption of thyroxine has been described in patients treated with drugs that modify an acidic environment.
Dr Marco Centanni and colleagues determined whether there is an increased need for thyroxine with euthyroid multinodular goiter and impaired secretion of gastric acid.
The research team assessed the dose of thyroxine required to obtain a low level of thyrotropin in 248 patients with multinodular goiter.
Of these 248 patients, 53 also had Helicobacter pylori-related gastritis and 60 had atrophic gastritis of the body of the stomach.
Of the 53 patients, 31 had evidence of infection and 29 were without such evidence.
The reference group comprised 135 patients with multinodular goiter and no gastric disorders.
|Omeprazole was associated with an increase in serum thyrotropin in all patients treated with thyroxine|
|New England Journal of Medicine|
In addition, variation in the level of serum thyrotropin was prospectively studied in 11 patients treated with thyroxine before and after H pylori infection.
The team also studied these levels both before and during treatment with omeprazole in 10 patients treated with thyroxine who had gastroesophageal reflux.
The daily requirement of thyroxine was higher in patients with H pylori-related gastritis, atrophic gastritis, or both conditions.
The researchers observed the occurrence of H pylori infection in the 11 patients treated with thyroxine led to an increase in the level of serum thyrotropin.
The team noted that this effect was nearly reversed on eradication of H pylori infection.
In a similar way, omeprazole treatment was associated with an increase in the level of serum thyrotropin in all 10 patients treated with thyroxine.
The team found that this effect was reversed by an increase in the thyroxine dose by 37%.
Dr Centanni's team concluded, “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.”