Stomach Acid May Affect Thyroid Drug

Doctors May Need to Adjust Thyroid Drug Dose in Patients With Stomach Problems

Medically Reviewed by Ann Edmundson, MD, PhD on April 26, 2006

April 26, 2006 -- Stomach conditions may undercut drugs that treat thyroid problems, a new study shows.

The study comes from researchers in Italy, including Marco Centanni, MD, of the endocrinology unit at Rome's La Sapienza University. Their report appears in The New England Journal of Medicine.

Centanni and colleagues studied 269 patients with harmless goiters, or enlarged thyroid glands. The thyroid is a butterfly-shaped gland at the base of the neck. Sometimes it becomes swollen and develops bumps but continues to make a normal amount of hormone. Thyroid hormone affects almost all of the body's metabolic processes.

The patients in Centanni's study were taking a drug called thyroxine, which is the main hormone made by the thyroid. This drug is sometimes used to shrink thyroids back to a normal size. Thyroid drugs are usually taken for other reasons, such as treating underactive thyroids. Find Tips for Sleeping Safely Without Heartburn.

Centanni's study shows that patients whose stomach acid secretion was altered by drugs, inflammation, or infection needed a higher thyroxine dose than those with normal acid secretion.

About the Study

The participants in the study included 123 patients who also had recurrent heartburn, gastritis (an inflammation, irritation, or erosion of the stomach's lining), or infection with Helicobacter pylori (H. pylori) -- which are bacteria linked to stomach ulcers. For comparison, the researchers also studied 135 patients with goiters but no stomach problems.

The average thyroxine dose needed by the patients with stomach problems was 22% to 34% higher than the average dose required by the comparison group.

Use of Stomach Acid Drugs

A closer look at 11 patients added more information about the role of drugs that treat stomach acid problems.

Those patients developed H. pylori infection after the study started, and they began taking drugs to treat that infection. Those drugs included omeprazole, which is found in the heartburn drug Prilosec and its generic versions.

Those patients needed a higher thyroxine dose when they started taking omeprazole, the study shows.

Low levels of stomach acid may bump up the required thyroxine dose, the researchers write. Their study also shows that patients generally followed recommendations to take thyroxine while fasting and wait at least an hour before eating or drinking to avoid having the drug interact with food.

If you're taking thyroid drugs and you have condition that affects stomach acid or you are taking medicines that affect stomach acid, consult a doctor with any questions about your drug doses. Never change drug doses on your own.

Show Sources

SOURCES: Centanni, M. The New England Journal of Medicine, April 27, 2006; vol 354: pp 1787-1795. WebMD Medical Reference: "Understanding Thyroid Problems -- the Basics." WebMD Medical Reference provided in collaboration with The Cleveland Clinic: "Digestive Diseases: Gastritis." WebMD Medical Reference: "Understanding Ulcers -- the Basics."

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