Original ArticleEffect of Proton Pump Inhibitors on Serum Thyroid-Stimulating Hormone Level in Euthyroid Patients Treated with Levothyroxine for Hypothyroidism
Section snippets
INTRODUCTION
Hypothyroidism is a common medical condition that is easily treated with thyroid hormone replacement, and thyrotropin (thyroid-stimulating hormone or TSH) is the laboratory study that is monitored to assess the adequacy of replacement.
Several medications are known to affect the level of serum thyroid hormone in patients with hypothyroidism receiving levothyroxine (LT4) replacement, either by reducing gastrointestinal absorption of LT4 1., 2., 3. or by increasing its metabolic clearance (4).
Patient Population
We collected our data using electronic review of medical records, which enabled us to access data regarding patients who were treated for primary hypothyroidism at Queens Hospital Center, Jamaica, New York, during the period between December 2002 and August 2005. Approval for the study was granted from the Institutional Review Board of Queens Hospital Center and Mount Sinai School of Medicine. The first 92 patients meeting all inclusion and exclusion criteria (see subsequent material) were
RESULTS
The baseline variables in the 2 groups, including mean TSH levels, age, body mass index, and LT4 dose, did not differ statistically between the 2 groups (Table 1).
In the study group, the baseline mean TSH value was 2.34 ± 1.3 μIU/mL, and the mean TSH value after taking lansoprazole for 2 to 6 months and the same dose of LT4 was 3.0 ± 2.2 μIU/mL. This represented a mean change of 0.69 ± 1.9 μIU/mL (P = 0.035) (Fig. 1), with the post-PPI TSH levels ranging from 0.09 to 8.0 μIU/mL (Table 2). In
DISCUSSION
To our best knowledge, this is the first study in humans with primary hypothyroidism receiving LT4 replacement therapy to demonstrate that a PPI (in this study, lansoprazole) affects the TSH level in such patients. Our patients were euthyroid, clinically and biochemically, during treatment with a stable dose of LT4 for at least 6 months preceding the initiation of lansoprazole therapy. This study showed that the mean TSH level increased after 2 to 6 months of lansoprazole therapy. In the study
CONCLUSION
To the best of our knowledge, this is the first study in humans with hypothyroidism receiving LT4 replacement demonstrating the effect of a PPI on serum TSH levels. On the basis of our findings, PPIs should be added to the list of medications potentially affecting the level of thyroid hormone in patients with hypothyroidism treated with LT4 replacement. Patients with hypothyroidism and normal TSH values during LT4 replacement therapy may need to undergo additional thyroid function testing after
DISCLOSURE
The authors have no conflicts of interest to disclose.
ACKNOWLEDGMENT
We acknowledge and thank Jihye Ann, PharmD, for data collection and Ruth Hoffenberg, the director of Queens Hospital Center Medical Library, for providing reference resources.
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