Clinical Thyroidology® for the Public

Summaries for the Public from recent articles in Clinical Thyroidology
Table of Contents | PDF File for Saving and Printing

HYPOTHYROIDISM
Use of proton pump inhibitors and levothyroxine

12

Instagram Youtube LinkedIn Facebook X

BACKGROUND
Levothyroxine is the most commonly used medication to treat hypothyroidism. Levothyroxine is usually taken in pill form. After swallowing the levothyroxine, the pill then dissolved in the stomach by the stomach acids and then absorbed intothe bloodstream in the small intestine. We know that some gastrointestinal conditions can affect the levothyroxine absorption; for example, celiac disease and inflammatory bowel disease. Certain medications can decrease the absorption of levothyroxine in the instestines. One such class of medications are proton-pump inhibitors (PPIs) which lower the amount of acid the stomach makes and are an effective treatment for reflux disease. Because of the decrease in the stomach acid, the levothyroxine pill may not be dissolved completely and the absorption of the levothyroxine may be decreased. Thus, patients may need frequent adjustments of their levothyroxoine treatment dose.

One brand of levothyroxine, Tirosint, is liquid that can be taken in a gelcap or as a liquid (Tirosint-SOL). Since the liquid form does not need to be dissolved, then the effect of PPIs on levothyroxine absorption should be minimal. In this study, the authors wanted to find out if PPIs affect the absorption of liquid levothyroxine (Tirosint- SOL).

THE FULL ARTICLE TITLE
 Seng Yue C et al. Proton pump inhibitors do not affect the bioavailability of a novel liquid formulation of levothyroxine. Endocr Pract 2024;30(6):513-520; doi: 10.1016/j. eprac.2024.03.388. PMID: 38554774.

SUMMARY OF THE STUDY
The authors studied 36 healthy men and women. They were divided in three groups: Group 1: took a single dose of 600 mcg of liquid levothyroxine together with 40 mg of omeprazole (a PPI). Group 2: took liquid levothyroxine in the morning and omeprazole in the evening. Group 3: took liquid levothyroxine alone. Blood samples to measure a thyroid hormone (total thyroxine, TT4) were taken before, and then at different time intervals up to 48 hours after taking the liquid levothyroxine dose.

The average age of the participants was 40 years old. The baseline TSH was 1.75 mIU/L. Most of the participants were male and white. The levels of TT4 were similar in the three groups: there was no difference in the TT4 levels in the participants taking liquid levothyroxine together with PPIs or after spacing their intake by several hours, as compared to the levels of the participants taking liquid levothyroxine only.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
Even though previous studies suggest that PPIs affect levothyroxine absorption, this small study shows that the absorption of liquid levothyroxine is not affected by PPIs. This study suggests that liquid levothyroxine may be a better treatment option for patients with hypothyroidism that are also taking medications such as PPIs. This may be especially important for patients who are not taking PPIs on a regular basis, but on and off, as it is often the case, and in this way, avoid swings of the thyroid levels.

— Susana Ebner MD

ABBREVIATIONS & DEFINITIONS

Primary hypothyroidism: the most common cause of hypothyroidism cause by failure of the thyroid grand.

Levothyroxine (T4): the major hormone produced by the thyroid gland and available in pill form as Synthroid™, Levoxyl™, Tyrosint™ and generic preparations.

Thyroid hormone therapy: patients with hypothyroidism are most often treated with Levothyroxine in order to return their thyroid hormone levels to normal. Replacement therapy means the goal is a TSH in the normal range and is the usual therapy. Suppressive therapy means that the goal is a TSH below the normal range and is used in thyroid cancer patients to prevent growth of any remaining cancer cells.

Table of Contents | PDF File for Saving and Printing