Levothyroxine absorption is impaired by many GI conditions, including:
- Atrophic gastritis,
- Chronic proton pump inhibitor use,
- Helicobacter pylori infection.
- Celiac disease
- IBD
- etc.)
When H. Pylori is the cause of poor absorption, treatment of H. pylori infection reverses this effect. After eradication of H. Pylori, a reduction of the levothyroxine dose by 30% or more will often be required.
Further Reading / Reference
Guidelines for the treatment of hypothyroidism: Prepared by the American Thyroid Association task force on thyroid hormone replacement. Thyroid 2014;24(12):1670-1751.
Helicobacter pylori infection and drugs malabsorption. World J Gastroenterol 2014;20(30):10331-10337.