Elsevier

Endocrine Practice

Volume 13, Issue 4, July–August 2007, Pages 345-349
Endocrine Practice

Original Article
Effect of Proton Pump Inhibitors on Serum Thyroid-Stimulating Hormone Level in Euthyroid Patients Treated with Levothyroxine for Hypothyroidism

https://doi.org/10.4158/EP.13.4.345Get rights and content

ABSTRACT

Objective

To examine retrospectively the effect of proton pump inhibitors (PPIs) on thyrotropin (thyroid-stimulating hormone or TSH) values in patients with hypothyroidism and normal TSH levels receiving levothyroxine (LT4) replacement therapy.

Methods

The data collection was done by retrospective review of electronic medical records from the period of December 2002 to August 2005 from patients with hypothyroidism who were receiving at least 25 μg of LT4 replacement daily at Queens Hospital Center. The first 92 patients meeting all inclusion and exclusion criteria were included in the study. The study group (N = 37) patient data were collected by selecting euthyroid patients who had received stable LT4 replacement for at least 6 months and in whom PPI therapy (lansoprazole) was later initiated. TSH levels were collected before and at least 2 months after the PPI treatment was started. The control group (N = 55) patient data were collected by reviewing TSH levels among euthyroid patients with a history of hypothyroidism receiving stable LT4 therapy and not receiving a PPI during the period of data collection. The statistical analysis was done by comparing the mean change in TSH level in each group with use of the Student t test.

Results

In the study group, the mean change in the TSH level from before to at least 2 months after initiation of PPI therapy, 0.69 ± 1.9 μIU/mL, was statistically significant (P = 0.035). In the control group, the mean change in the TSH level during the study period, 0.11 ± 1.06 μIU/mL, was not statistically significant (P = 0.45).

Conclusion

To our best knowledge, this is the first study in humans with hypothyroidism demonstrating the effect of PPIs on serum TSH levels. PPIs should be added to the list of medications 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 additional thyroid function testing after treatment with PPIs and may need adjustment of their LT4 dose. (Endocr Pract. 2007;13:345-349)

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.

REFERENCES (14)

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