The tiny thyroid gland could have a big impact on heart health, new research suggests.
Middle-aged and older adults with an elevated thyroid hormone may be at higher risk of heart disease and death, researchers found.
In the new Dutch study, high and even high-normal levels of a hormone called free thyroxine (FT4) doubled the odds of having calcification of the coronary arteries. This can be a sign of atherosclerosis, commonly called hardening of the arteries.
Higher FT4 levels were also linked to an 87 percent greater risk of having a heart attack or stroke and twice the risk of dying from one.
“High FT4 is indicative of an overactive thyroid,” explained lead researcher Dr. Arjola Bano, of Erasmus University in Rotterdam.
FT4 is produced in the thyroid gland at the front of the neck. It helps control the body’s rate of energy use, she said.
Atherosclerosis means you have fatty deposits called plaque that can clog arteries. As plaque builds up, the artery narrows, reducing blood flow.
Atherosclerosis can progress from thickening and hardening of the artery walls to heart disease, stroke and death, Bano said.
“Our findings suggest that FT4 measurement can help identify people at increased risk of atherosclerotic events,” she added.
But before doctors start testing people for their FT4 levels, the findings need confirmation in broader population groups, Bano said. This research was restricted to mostly white participants aged 45 or older.
One doctor who reviewed the findings agreed that more study is needed.
This study shows an association, but doesn’t prove that FT4 boosts the risk for heart disease, said Dr. Byron Lee, director of electrophysiology laboratories at the University of California, San Francisco.
“The FT4 could be the cause or simply a marker,” Lee said. “Either way, this warrants further exploration, and patients with high FT4 should be on the lookout.”
Dr. Minisha Sood is an endocrinologist at Lenox Hill Hospital in New York City who also reviewed the findings.
She explained that “thyroid hormone is known to increase production of damaging compounds and to foster an environment in the body” that encourages blood clots.
“In an environment of inflammation, which is also possibly a contribution by high thyroid hormone levels,” this could help lead to heart disease, Sood said.
But she too stressed that the study couldn’t yet prove cause and effect.
For the study, Bano and her colleagues tracked data on more than 9,400 participants in the Rotterdam Study, an ongoing research project in the Netherlands. Average age of the participants was 65.
The researchers looked at two types of hormones — thyroid-stimulating hormone and FT4.
They also looked for evidence of atherosclerosis and death from heart disease, stroke or other arterial disease.
In addition, they evaluated coronary artery calcification scores, to determine if patients had atherosclerosis without symptoms.
Follow-up averaged nearly nine years. During that time, 612 patients died of heart disease, while 934 had a heart attack or stroke, the researchers found.
The team concluded that mechanisms other than traditional heart risk factors might have played a role in those outcomes. Perhaps preventive measures targeting thyroid function could help reduce heart attack and stroke rates, they suggested.
The report was published online Oct. 31 in the journal Circulation Research.
For more on overactive thyroid, visit the American Thyroid Association.