American Thyroid Association

American Thyroid Association

November 01, 2019
2 min read

Levothyroxine frequently prescribed despite lack of testing

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CHICAGO — Levothyroxine is prescribed to more than 80% of patients despite a lack of supporting evidence from thyroid function laboratory assessments, according to findings presented at the annual meeting of the American Thyroid Association.

Philip G. Clerc

Philip G. Clerc, MD, of the endocrinology service at Brooke Army Medical Center in San Antonio, and colleagues analyzed the testing frequency of thyroid-stimulating hormone, free thyroxine and thyroid peroxidase antibodies in 22,131 adults who were prescribed levothyroxine for the first time in 2018 using data from the Military Health System. The researchers found that these thyroid function tests were conducted for only 4843 individuals. For patients at military facilities, 27% received testing. For patients at network facilities, 21% received testing.

“There is always a concern that data out is only as good as data in. Maybe there is some issue with insurance billing and CPT codes,” Clerc told Endocrine Today. “That is not the primary focus of the study, but it was very alarming that perhaps 75% of patients aren’t even getting tested for one of these three labs, which are the main labs we use.”

Clerc and colleagues also found that for only 58 of the 358 patients who had test values available did the result meet ATA/American Association of Clinical Endocrinologists’ guideline standards for levothyroxine use. Of those 58, 29 had overt hypothyroidism, 14 had subclinical hypothyroidism and a TSH level of 10 mIU/L or more and 15 had subclinical hypothyroidism and a TSH level of less than 10 mIU/L, including 12 who also had atherosclerotic cardiovascular disease, two who had thyroid peroxidase antibodies and one who had heart failure.

“Of those patients that had labs, most of them shouldn’t have been started on the medication,” Clerc said. “Only 16% made a really good indication for therapy.”

Clerc also noted that 66% of patients who were diagnosed with subclinical hypothyroidism but should not have received levothyroxine were aged 65 years or older. In addition, Clerc and colleagues found that among those who received a prescription for levothyroxine, overt or subclinical hyperthyroidism was identified in 22 patients (6%), which meant “they definitely should not have gotten a medication.” – by Phil Neuffer with additional reporting by Jill Rollet


Clerc P, et al. Poster 60. Presented at: 89th Annual Meeting of the American Thyroid Association; Oct. 30-Nov. 3, 2019; Chicago.

Disclosure: Clerc reports no relevant financial disclosures.