Most elderly patients with subclinical hypothyroidism do not need to be treated

To the Editor: I appreciate the review by Dr. Xu and colleagues¹ and accompanying editorial by Dr. Mammen² on management of subclinical hypothyroidism in elderly patients published in the April issue. I feel, however, the scope of the problem extends beyond this population.

In many cases, the purported benefits of treating subclinical hypothyroidism are minimally supported and the potential risks underappreciated. Analysis of data from a large cohort of adults who filled levothyroxine prescriptions between 2008 and 2018 showed that about 80% of new prescriptions were for people with normal thyrotropin levels or in the mild subclinical hypothyroidism range, with treatment increasingly coming from clinicians not in the traditional realms of endocrinology and primary care.³ The overwhelming majority of these patients were under 65.

Mammen and colleagues⁴ have previously described the disconcerting prevalence and duration of iatrogenic hyperthyroidism in the elderly, particularly disproportionate in women who are already at higher risk for osteoporosis, only heightened by an inappropriate thyrotropin suppression. How commonly this occurs in the younger population is largely speculative, though older work has suggested that at least 10% of those prescribed levothyroxine have some degree of overly suppressed thyroid-stimulating hormone and 2.5% have induced overt thyrotoxicosis.⁵ This is likely why such a considerable proportion of people can have levothyroxine safely discontinued, much more so in those with subclinical hypothyroidism.⁶

The overprescribing of levothyroxine and overtreatment of subclinical hypothyroidism are quintessentially low-value care endemic in the United States and, given the scale of impact, warrant more discussion at the national level as we look for ways to catch up with the rest of the world in our value-based healthcare delivery efforts.

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