BACKGROUND
Hypothyroidism, or an underactive thyroid, is very common. Treatment is usually in the form of thyroid hormone replacement in the form of levothyroxine (L-T4). Currently, L-T4 comes mainly in the form of solid tablets. The exception to this is Tirosint, which is a gelatin pill containing liquid L-T4.

L-T4 tablets need an acidic stomach to be best absorbed. Proton pump inhibitors (PPI’s) are very commonly used medications to decrease the stomach acid and can cause poor L-T4 absorption. This leads to an increase in TSH and the need to adjust the L-T4 dose. Patients may need more frequent tests and dose changes to find the right L-T4 dose. There are few reports that absorption of L-T4 in the form of Tirosint may not be affected as much from acid changes in the stomach.

The authors designed this study to find out the effects of switching from a standard L-T4 tablet to the same dose of L-T4 soft capsules in patients whose thyroid glands were removed and who were taking PPI’s.

THE FULL ARTICLE TITLE
Sachmechi I et al. Efficacy of levothyroxine sodium soft gelatin capsules in thyroidectomized patients taking proton pump inhibitors: an open-label study. Thyroid 2023;33(12):1414-1422; doi: 10.1089/thy.2023.0382. PMID: 37885233.

SUMMARY OF THE STUDY
Adults with a history of hypothyroidism due to removal of their thyroid were studied. Patients were taking different brand or generic forms of L-T4 tablets with a dose between 88 and 250 mcg/day. Their thyroid tests were stable for at least 6 weeks and TSH level was between 0.3 and 4 mIU/L. They were on long term PPI treatment for gastroesophageal reflux (GERD) or other diseases.

Patients with other conditions known to effect L-T4 absorption were excluded. After 4-6 weeks they were switched to Tirosint soft capsules at the same dose and thyroid tests were done at 6 and 12 weeks. L-T4 dose change was permitted if necessary due to low or high TSH levels.

Out of the 47 patients included, 45 completed the study. Patients were around 55 years old; most were women. Average thyroid hormone dose was 144.54 mcg daily. Overall, after the patients switched from L-T4 tablets to soft gelatin capsules at the same dose, the TSH level significantly decreased and thyroid hormones increased by 6 weeks and even more at 12 weeks, especially in those who did not miss any doses.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study showed that in patients who had their thyroid gland removed and needed to take PPI’s and were also taking L-T4 tablets, switching to soft gelatin capsules caused an increase in thyroid hormone levels and a decrease in TSH. This study did not have a lot of patients, there was no control group to confirm the results, and whether there was a difference in symptoms of hypothyroidism was not checked. Regardless, the findings of this study are important for patients who are having problems with keeping thyroid hormone levels under control while taking PPI’s. Soft gelatin capsules may be an alternative to increasing monitoring frequency to adjust L-T4 tablet dosage. These formulas may cost several times more than the standard tablets and patients should have a discussion with their doctors to decide whether this is a good option for them. We still need more studies to find out whether this strategy is safe, cost-effective and more beneficial.

— Ebru Sulanc, MD

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