Despite conflicting guidelines on how to treat hypothyroidism, U.S. physicians prescribe combination therapy more often than physicians around the world.
Despite conflicting guidelines on how to treat hypothyroidism, U.S. physicians prescribe combination therapy-adding synthetic liothyronine (LT3) to standard therapy with synthetic levothyroxine (LT4) replacement-more often than physicians around the world.
Both physician characteristics and patient characteristics profoundly affect physician prescribing patterns, according to two new surveys.
The results of this 2017 survey suggest that “approximately one-third of physicians taking care of patients with hypothyroidism are willing to prescribe therapies other than levothyroxine (LT4),” stated the authors, led by Jacqueline Jonklaas, M.D., Ph.D., of Georgetown University Medical Center, Washington, D.C.
In 2012 and 2014, the American Thyroid Association (ATA) guidelines for the treatment of hypothyroidism stated there was insufficient evidence to support routine prescribing of T3-containing therapies. More recent recommendations from British and Italian societies suggest that T3-containing therapies can be considered.
In the 2017 physician survey, ATA members were presented with 13 different theoretical patients with hypothyroidism and asked to choose among six therapeutic options, including levothyroxine, synthetic combination therapy, thyroid extract, and liothyronine monotherapy. The 13 patient scenarios incorporated parameters that provided potential reasons for considering combination therapy, for example, presence of symptoms, low serum triiodothyronine concentration, and documentation of deiodinase polymorphisms.
Of the 389 survey respondents, 93% prescribed therapy for hypothyroidism. About half (53%) of respondents had been in practice for more than 20 years, and about one-quarter (23%) had been in practice for 11 to 20 years. Two thirds (64%) practiced in North America and 18% practiced in Europe; 85% were endocrinologists and 5% were surgeons.
In multivariate analysis looking at the characteristics of physicians published online Dec. 17, 2018 in Thyroid, physicians from North America were both more likely to prescribe any triiodothyronine-containing therapies and more likely to add liothyronine to levothyroxine therapy. In addition, they were more likely to prescribe desiccated thyroid extract or liothyronine monotherapy.
“The current multivariate analysis shows that physician characteristics affect prescribing patterns,” stated the authors.
They suggested this may be due to the impact upon physicians of patient-related experiences, media exposure, influence from pharmaceutical companies, educational activities, or other concerns. “These results have potential importance for understanding physician–patient interactions at a time when the benefits and risks of triiodothyronine-containing therapies have not been fully documented,” they stated.
In an earlier analysis looking at patient characteristics associated with prescription of combination therapy, published online Nov. 12, 2018 in Thyroid, the authors stated that “most endocrinologists encounter patients who are dissatisfied with their current hypothyroidism therapy and request combination therapy with either liothyronine (LT3) or thyroid extract.”
They reported that key significant factors were patients’ symptoms, T3 levels, thyroid-stimulating hormone levels, presence of a polymorphism, and the patient's request for T3 therapy.
The authors concluded “this analysis appears to show a marked increase in the willingness of physicians to prescribe combination therapy in specific circumstances. If current prescribing patterns do incorporate the use of therapies other than LT4, there is a critical need for more research into the benefits and risks of these therapies.”
Jacqueline Jonklaas, Eshetu Tefera and Nawar Shara. "Prescribing Therapy for Hypothyroidism: Influence of Physician Characteristics," Thyroid. Jan. 23, 2019. https://doi.org/10.1089/thy.2018.0369