Reversible normalisation of serum TSH levels in patients with autoimmune atrophic gastritis who received L-T4 in tablet form after switching to an oral liquid formulation: a case series

Background: L-thyroxine (L-T4) malabsorption is a potential concern in patients with autoimmune atrophic gastritis. Methods: We evaluated five patients with autoimmune gastritis, who showed high serum thyrotropin (TSH) levels (in the hypothyroid range) while in therapy with L-T4 in tablet. All patients were switched to receive an oral L-T4 liquid formulation maintaining the same dosage. Results: In all patients who received L-T4 in tablet form after switching to an oral liquid formulation with the same L-T4 dosage, TSH circulating levels were normalized. In four patients who were switched back again to receive L-T4 in tablets, maintaining the dosage, TSH levels worsened again reaching levels in the hypothyroid range. Conclusions: The fact that the change from tablets to liquid oral formulation normalised serum TSH levels, and that switching back to tablets caused thyrotropin levels to worsen, leads us to believe that absorption of L-T4 is greater with oral liquid formulations in these patients. These results suggest that the L-T4 oral liquid formulation could circumvent the pH alteration resulting from atrophic gastritis.