Plate Nº 69 · recorded November 9, 2026
Health & Medicine ResearchReported finding
Out-of-range thyroid levels linked to higher cardiovascular death risk
Among more than 705,000 U.S. veterans on thyroid hormone treatment, TSH below 0.1 was linked to a 39% higher cardiovascular death rate, while levels above 20 carried more than double the rate.
By Marcus Bennett4 min read732 words
In brief
- More than 705,000 U.S. veterans were studied from 2004 through 2017, with a median follow-up of four years.
- About 11% of participants died from cardiovascular causes during follow-up.
- TSH below 0.1 was linked to a 39% higher relative cardiovascular death rate than the reference range.
- TSH above 20 was linked to more than twice the cardiovascular death rate of the reference group.
- The study appeared in JAMA Network Open in 2022; comparisons accounted for age, smoking and previous heart problems.
By Marcus Bennett
In a study of more than 705,000 U.S. veterans, people taking thyroid hormone treatment had a 39% higher relative rate of cardiovascular death when thyroid-stimulating hormone, or TSH, fell below 0.1 rather than sitting inside the study’s reference range.
That association did not mean every person with a low result would die from a heart-related cause. Researchers from the University of Michigan and Veterans Affairs Ann Arbor Healthcare System reported the record-based observational study in JAMA Network Open in 2022.
What did the study find?
Researchers reviewed records for adults receiving thyroid hormone treatment between 2004 and 2017. Median follow-up was four years. Across the full population, about 11% died of cardiovascular causes, including heart attack, heart failure, or stroke, during follow-up.
Compared with results within the study’s reference range:
- TSH below 0.1 was linked to a 39% higher relative rate of cardiovascular death.
- TSH above 20 was linked to more than twice the rate.
- Free thyroxine measurements showed a similar pattern at both the low and high extremes.
The researchers compared rates after accounting for age, smoking, and previous heart problems. The 39% figure compares groups; it does not mean each low result added 39 percentage points to an individual’s risk. Accounting for these factors cannot, by itself, prove that thyroid levels caused the deaths.
Takeaway: Both unusually low and unusually high thyroid-test results were associated with worse cardiovascular outcomes.
How do the thyroid blood tests work?
Levothyroxine replaces a hormone that the thyroid gland would normally make. The body uses thyroid hormone to regulate how quickly it uses energy, and changes in hormone levels can affect the heart and blood vessels. Blood-test results therefore help clinicians assess the prescription alongside the patient’s symptoms and health.
One test measured TSH. The pituitary gland releases this hormone to tell the thyroid how much hormone to make. Its level usually falls when the body has more thyroid hormone than it needs, while a high TSH result can point to too little thyroid hormone.
The team also examined free thyroxine, a direct measure of the thyroid hormone circulating in the blood and available to tissues. As with TSH, free thyroxine showed a similar cardiovascular-death pattern at both extremes.
Because patients could have several tests over the years, the analysis treated results as measures that could change over time. It did not assign each person one fixed thyroid status for the entire study.
Takeaway: Repeated thyroid tests give clinicians a changing picture of whether treatment remains aligned with the patient’s needs.
Does this prove that changing a dose will reduce risk?
No. The study could not show how much of the risk would change after a dose adjustment. Its records could reveal the association but not the full sequence of events behind it.
Medical records cannot always show why a person’s levels were out of range or whether another illness influenced both the test results and the risk of death. The researchers excluded some conditions and medications that can complicate thyroid testing, but those steps do not remove every possible alternative explanation.
Most participants were men, and the median age was 67. The findings may apply differently to younger adults and to groups that were less well represented in the study. The large sample therefore does not settle how the association varies across populations.
Takeaway: The numbers identify a clinical signal, not a proven benefit from changing treatment.
What should clinicians do with the finding?
The practical message is to review blood-test results as thyroid hormone treatment continues. A clinician can use TSH or free thyroxine results to assess whether the current dose is meeting the patient’s needs, then weigh those results alongside symptoms, other medicines, and changes in health.
For practitioners, the finding adds a monitoring checkpoint rather than an automatic dosing rule. It supports asking whether the current prescription still fits the available laboratory and clinical evidence.
Separately, researchers are exploring the combination of heart tests with artificial intelligence to predict sudden cardiac death. The thyroid study did not evaluate that technology.
Takeaway: Use out-of-range results to prompt monitoring and interpretation, not automatic dose changes.
Bottom line: The study links out-of-range thyroid tests with higher cardiovascular death rates, while leaving the effect of correcting them unproven.
via knowridge.com (Source)
More from Marcus Bennett
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News editor covering regulation, policy and their impact on general science news at SciBeat.
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