By Sara Hover, RPh, FAARM, PCCA Clinical Compounding Pharmacist
 

Many patients struggle with optimizing thyroid hormone levels due to issues with absorption. As discussed in many articles, the most common factors to consider are interactions with nutrients and/or medication as well as drug adherence. These factors are considered “pseudomalabsorption,” contrasting with malabsorption, which is due to the small intestine not functioning properly.¹

As pharmacists, we should always be looking to the literature for new ideas to potentially help patients with thyroid absorption. Three recent journal articles offer some promising insights. First, a recent study suggests that an additional cause of pseudomalabsorption may be the storage conditions of the medication.² Another interesting study demonstrates that a cause of malabsorption of thyroid hormones could be due to inflammatory bowel disease, like ulcerative colitis.³ Finally, a different study suggests that taking a deeper dive into the thyroid-gut axis and the effect of the microbiome on thyroid function might provide a novel approach to helping patients with thyroid issues.⁴

Storage

Recent guidelines recommend that “L-thyroxine [or levothyroxine] should be stored per product insert at 20–25° C (68–77° F) and protected from light and moisture.”² Storage of commercial products is often is overlooked when considering absorption issues, but the authors of a recent journal article suggest that when reviewing possible causes of refractory hypothyroidism, storage of the medication should be on the list. In their small study, Benvenga et al. (2017) observed that thyroid-stimulating hormone (TSH) levels returned to normal when the patients were more cautious about temperature and humidity exposure of their medication.² This is a simple and practical consideration that could benefit many patients.

Inflammatory Bowel Disease

The absorption of the thyroid hormone levothyroxine (T4) occurs in the small intestine, so any disorder that affects the intestinal tract could lead to T4 malabsorption. According to Virili et al. (2019), “Ulcerative colitis (UC) is an inflammatory bowel disease that has been postulated as a potential cause of the increased need for thyroxine.”³ They point out that gastrointestinal disorders may cause variation in drug dissolution or ionization status, which could possibly necessitate an increase in dose. Increased gut permeability caused by damage to the small intestine could also cause a reduction in transit time and alterations in electrolytes. These alterations could precipitate bacterial overgrowth, which would create nutrient malabsorption, worsening hypothyroidism. ³ This warrants further investigation into the role inflammatory bowel disease (IBD) plays in thyroid disease and its treatment.

Microbiome

Recent research by Knezevic et al. (2020) showed the beneficial effects of supplementation with prebiotics and probiotics in patients with hypothyroidism. They observed a reduction of TSH, an increase in free triiodothyronine (liothyronine, or T3), a reduction in the required T4 dose and a reduction in patient fatigue. They postulate that adjustments in the gut microbiota increases T4 availability, which stabilizes thyroid function.⁴

Another consideration is that the deconjugation of the thyroid hormone is regulated by bacterial enzymes. Probiotics also play a role in accumulating trace elements, such as selenium, zinc and copper, which are critical for thyroid function. Research is mounting that suggests a strong connection between the thyroid and the gut, referred to as the thyroid-gut axis. This correlation between the effect of gut bacteria on the immune system and thyroid function is not well known, but it is an immerging concept. More research will likely occur regarding the thyroid-to-gut link. This provides an excellent opportunity for pharmacists to encourage all patients, but especially patients struggling with thyroid dysfunction, to focus on gut health and recommend quality prebiotics and probiotics.

Key Takeaways

• Counsel patients about potential interactions between thyroid medication and nutrients or other medications
• Discuss proper storage of thyroid medication (avoid heat and humidity) with patients
• Patients with IBD could require a higher dose of T4 due to inflammation ³
• Probiotics may influence thyroid function, reduce TSH and increase free T3⁴

PCCA members can find additional information on this subject in Sara Hover’s article “Factors That Affect Thyroid Absorption” in the March 2014 issue of PCCA’s members-only magazine, the Apothagram.

Sara Hover, RPh, FAARM, has been a compounding pharmacist for over 20 years and joined the PCCA Clinical Services team in June 2013. Before joining the PCCA staff, she was the owner and pharmacist of Creative Compounds in Prosper, Texas, an independent, compounding-only pharmacy that focused on women’s health and nutrition. In addition to her expertise in hormone replacement therapy, Sara possesses a vast knowledge of homeopathics as well as herbal and vitamin supplements. Sara obtained her Bachelor of Science degree from the University of Texas at Austin in 1994. She is a lifetime member of the University of Texas College of Pharmacy Alumni Association.

References

1. Gonzales, K. M., Stan, M. N., Morris, J. C., III, Bernet, V., & Castro, M. R. (2019). The levothyroxine absorption test: A four-year experience (2015–2018) at the Mayo Clinic. Thyroid, 29 (12), 1734–1742. https://doi.org/10.1089/thy.2019.0256

2. Benvenga, S., Papi, G., & Antonelli, A. (2017). Refractory hypothyroidism due to improper storage of levothyroxine tablets. Frontiers in Endocrinology. https://doi.org/10.3389/fendo.2017.00155

3. Virili, C., Stramazzo, I., Santaguida, M. G., Bruno, G., Brusca, N., Capriello, S., Cellini, M., Severi, C., Gargano, L., & Centanni, M. (2019). Ulcerative colitis as a novel cause of increased need for levothyroxine. Frontiers in Endocrinology. https://doi.org/10.3389/fendo.2019.00233

4. Knezevic, J., Starchl, C., Tmava Berisha, A., & Amrein, K. (2020). Thyroid-gut-axis: How does the microbiota influence thyroid function? Nutrients, 12(6). https://doi.org/10.3390/nu12061769

These statements are provided for educational purposes only. They have not been evaluated by the Food and Drug Administration, and are not to be interpreted as a promise, guarantee or claim of therapeutic efficacy or safety. The references cited did not necessarily evaluate PCCA products or formulas included in these statements. The information contained herein is not intended to replace or substitute for conventional medical care, or encourage its abandonment.