Oral Liquid L-Thyroxine (L-T4) May Be Better Absorbed in Comparison to L-T4 Tablets in Patients With Lactose Intolerance

In patients with lactose intolerance (LI), L-thyroxine (L-T4) malabsorption is often present, that leads to the necessity to use elevated L-T4 doses in the substitutional treatment of hypothyroidism. After excluding non-compliance, the differential diagnosis should include such disorders as LI, atrophic gastritis, coeliac disease, and others. In case of a diagnosis of LI, a low lactose diet and a lactose-free L-T4 preparation should be administered, to decrease the dose of the L-T4 formulation, and restore euthyroidism. We report the normalisation of circulating thyrotropin (TSH) levels in 8 patients with LI who received L-T4 tablets, after switching to an oral liquid lactose-free formulation. After switching from oral tablets to the liquid L-T4 (at the same dose, 30 minutes before breakfast) TSH was significantly reduced (TSH, evaluated 1-3 months after the switch, decreased: from 7.5±3.1 to 3.2±2.4 μIU/mL, P<0.05). The return back to tablets (at the same dosage, 30 minutes before breakfast) caused thyrotropin levels to worsen again. This result leads us to believe that the absorption of oral liquid formulation of thyroxine is greater in these patients. In conclusion, these data suggest that the L-T4 oral liquid formulation could bypass the issue of malabsorption in patients with lactose intolerance.