Many older adults prescribed thyroid hormone plus drugs that interfere with thyroid tests
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Nearly one-third of older adults on thyroid hormone also take another medication that can interfere with thyroid function tests, particularly adults with multiple comorbidities, according to data presented at the ENDO annual meeting.
“Thyroid hormone use is common in older adults, and its management is complicated by the fact that many older patients often also use multiple medications for numerous chronic conditions,” Maria Papaleontiou, MD, an assistant professor in the division of metabolism, endocrinology and diabetes at the University of Michigan, told Healio. “This may increase the risk of drug interactions and the potential for side effects. It is important to be vigilant to ensure safe medication use in our older patients.”
Papaleontiou and colleagues conducted a population-based retrospective cohort study of adults aged 65 years and older using thyroid hormone replacement therapy. Data were obtained from the Corporate Data Warehouse of the Veterans Health Administration from 2004 to 2017 on the number of older adults on thyroid hormone also taking medications known to commonly interfere with thyroid function tests. Patient age, sex, race, ethnicity and number of comorbidities were also obtained.
“Prior studies have shown that thyroid hormone use is common, with levothyroxine being the most frequently prescribed medication in the United States between 2012 and 2016 and the third most frequently prescribed medication during 2017 and 2018,” Papaleontiou said. “Additionally, older age is a significant predictor for thyroid hormone initiation, with use continuing long term. Understanding the number of older adults and also specific subgroups of older adults who are on thyroid hormone and medications that interfere with thyroid function tests is key in raising awareness to ensure patient medication safety.”
There were 538,137 adults in the study cohort, of whom 31.6% were taking at least one medication that interferes with a thyroid function test during a median follow-up time of 56 months. Adults in race or ethnicity categories other than white were more likely to take an interfering medication compared with white participants (OR = 1.18; 95% CI, 1.15-1.21) and Hispanic adults had higher odds of using interfering medication than those who were not Hispanic (OR = 1.11; 95% CI, 1.08-1.14).
Women had a higher likelihood for interfering medication use compared with men (OR = 1.12; 95% CI, 1.08-1.15). People with a score of 2 or higher on the Charlson comorbidity index were more likely to use interfering medications than those with a lower score (OR = 2.47; 95% CI, 2.43-2.52). Adults aged 85 years or older were less likely to use an interfering medication compared with participants aged 65 to 74 years (OR = 0.47; 95% CI, 0.46-0.48).
“Even though we know that thyroid hormone use in older adults is common, the finding that one-third of them take medications interfering with thyroid function tests is not completely surprising as many older adults have comorbidities,” Papaleontiou said. “Less expected was the finding that older adults who are female, non-white and of Hispanic ethnicity were more likely to be on interfering medications.”
Papaleontiou said providers should discuss the appropriateness of medication use with older adults on thyroid hormone and target specific groups who are most vulnerable.
Perspective
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Jonathan D. Leffert, MD, FACP, FACE, ECNU
In this poster, Papaleontiou and colleagues found in a population-based, retrospective study of over 500,000 patients from the VA Database that approximately one-third of patients on thyroid hormone replacement were also taking interfering substances. The most common substances were prednisone, prednisolone, amiodarone, phenytoin and carbamazepine. Most of the patients in the study were men and had two or more comorbidities. The result showed in a multivariable logistic analysis, that women, in the 65- to 85-years age range, Hispanics and non-whites had the highest odds ratio of taking interfering substances while on thyroid hormone replacement.
This is a significant study which highlights the importance of clinicians looking closely, particularly in older patients, at all of the medications that patients are taking and to carefully follow thyroid function tests in those patients. Thyroid levels will often vary for many reasons. The importance of having an accurate and complete list of medications for each patient is emphasized by this study. In addition, if a medication that interferes with thyroid function is identified, an alteration in thyroid hormone levels may have significantly detrimental clinical effects on the patient. The results of this study also point to certain demographic groups that are particularly at risk for taking interfering substances so that our clinical awareness is ever vigilant, particularly in these patients.
Interfering substances make thyroid hormone replacement therapy a more complicated and potentially dangerous situation, particularly in older patients, with our role as clinicians to recognize that these substances are common and their effect can be profound.
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Beeson R, et al. Interfering medications in older adults on thyroid hormone replacement: who is at risk? Presented at: Endocrine Society Annual Meeting; March 20-23, 2021 (virtual meeting).
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