Serum TSH Levels Normalisation in Patients Affected by Autoimmune Atrophic Gastritis, After the Switch From Oral L-T4 in Tablet Form to L-T4 in Liquid Formulation

Abstract Patients affected by autoimmune atrophic gastritis could have some issues in L-thyroxine (L-T4) absorption, due to drug malabsorption, induced by the increased gastric pH. Different factors influence L-T4 absorption, such as dietary habits, interference with other drugs, absorption kinetics, age of the patient, adherence to therapy, and others. We enrolled 36 patients affected by autoimmune atrophic gastritis with high serum thyrotropin (TSH) levels under therapy with L-T4 in the tablet formulation. L-T4 tablets were changed to an oral liquid L-T4 preparation, maintaining the same dose. The switch from L-T4 in tablet formulation to the liquid one, at the same L-T4 dosage, led to the normalisation/reduction of circulating TSH levels. Then 14 patients, who were switched back again to receive L-T4 in tablets (with the same dose), had a worsening of TSH values, falling in the hypothyroid range. In conclusion, our findings led to hypothesize that the pH alteration issue caused by autoimmune atrophic gastritis could be overcome by the oral L-T4 liquid formulation administration.