Send to

Choose Destination
Endocr Pract. 2014 Mar;20(3):e38-41. doi: 10.4158/EP13316.CR.

Tablet levothyroxine (L-T4) malabsorption induced by proton pump inhibitor; a problem that was solved by switching to L-T4 in soft gel capsule.

Author information

Endocrinology, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy.
Endocrinology, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy Master Program on Childhood, Adolescence & Women's Endocrine Health, University of Messina, Messina, Italy Interdepartmental Program of Molecular and Clinical Endocrinology and Women's Endocrine Health, A.O.U. Policlinico G. Martino, Messina, Italy.



To report a patient in whom the impaired absorption of tablet levothyroxine (L-T4) due to a proton pump inhibitor (PPI) use was corrected by switching the patient to the soft gel capsule.


A woman with Hashimoto's thyroiditis-associated hypothyroidism (serum thyroid-stimulating hormone [TSH] 6.8-9.6 mU/L) had been treated with tablet L-T4 (100 μg/day). Because she used to take pantoprazole just before L-T4 in the morning, TSH failed to normalize (4.4-6.5 mU/L). Thus, the daily dose had been progressively increased to 125 and 150 μg/day, with serum TSH levels of 2.4 and 0.6 mU/L, respectively.


While maintaining pantoprazole, we switched the tablet L-T4 (150 g/day) to a soft gel capsule (125 μg/day; Tirosint® capsule, IBSA, Lugano, Switzerland) and after 2 months, to 100 μg/day. Serum TSH was lower than under the equivalent regimens with the tablet: 0.5 versus 2.4 mU/L (125 μg/day) and 2.4 versus 4.4 to 6.5 mU/L (100 μg/day). Upon switching back to the tablet (100 μg/day), serum TSH increased to 3.2 and 4.7 mU/L and then dropped to 2.7-3.0 mU/L when the dose was increased to 125 μg/day. We also acutely evaluated the intestinal absorption of L-T4 by administering 600 μg LT4 as a tablet or soft gel capsule while maintaining pantoprazole. Pharmacokinetic indices showed better and faster absorption for the soft gel capsule versus tablet (area under the curve [AUC]0-4h = 16,240 vs. 10,960 nmol/L x 4 hours, maximum absorption [Cmax] = 108 vs. 73 nmol/L, and time of maximum absorption [Tmax] = 120 minutes vs. 180 minutes).


Confirming in vitro studies conducted by other authors, the soft gel capsule L-T4 is negligibly affected by changes in gastric pH compared to tablet L-T4.


Supplemental Content

Full text links

Icon for Allen Press, Inc.
Loading ...
Support Center