Study Challenges Standard Testing for Hypothyroid Patients
A new study published in PLOS One, co-authored by Theodore C. Friedman, MD, PhD, Chair of the Department of Internal Medicine at Charles R. Drew University of Medicine and Science (CDU), is bringing fresh attention to a long-overlooked lab test that may help explain why some patients with hypothyroidism continue to feel tired—despite being on standard thyroid medication.
The peer-reviewed study looked at nearly 1,000 patients treated for low thyroid function over an 11-year period. Researchers focused on a hormone called reverse T₃ (rT₃), which isn’t typically checked in routine care but may play an important role in lingering symptoms in hypothyroid patients, like fatigue.
Dr. Friedman and his team found that patients taking the standard medication, levothyroxine (known as L-T₄), were more likely to have high levels of reverse T₃. By contrast, patients on other therapies that included T₃—such as desiccated thyroid extract (DTE) or L-T₄ plus liothyronine (L-T₃) —had much lower levels. The findings suggest that standard treatment may not work equally well for everyone.
“I was inspired to figure out why my patients with underactive thyroids aren’t doing well, even though they’re on what’s considered optimal thyroid hormone replacement,” said Dr. Friedman. “I wanted to look at this sort of old test and see if it can explain why these patients have fatigue.”
Reverse T₃ is often viewed as outdated and rarely tested in conventional medicine, but Dr. Friedman believes it’s worth reconsidering. “There are articles that came out saying we shouldn’t be measuring this,” he said. “But the test is important, especially in patients who aren’t doing well on optimal replacement.”
One of the study’s more surprising discoveries was just how common elevated rT₃ levels were in patients on L-T₄-only therapy. “Most of the high reverse T₃ was seen in those patients,” Dr. Friedman said. “People not on any thyroid medicine usually had pretty good levels.”
The study doesn’t claim that high reverse T₃ is the direct cause of fatigue, but it opens the door to more personalized treatment strategies. Dr. Friedman plans to follow up with a study that tracks patient symptoms alongside rT₃ levels to better understand whether changing medications guided by rT₃ levels can improve quality of life.
As CDU continues to advance research that addresses health disparities and improves outcomes for underserved communities, this study encourages providers to take a closer look at how long-standing treatment norms may affect patient well-being.
The full study, “Reverse T3 in patients with hypothyroidism on different thyroid hormone replacement,” is available now in PLOS One.
PLOS One is a peer-reviewed journal published by the Public Library of Science.