Even subclinical hyperthyroidism can weaken bones

Even subclinical hyperthyroidism can weaken bones

Subclinical hyperthyroidism may be an independent risk factor for fractures, a community-based cohort study found.

In the analysis of nearly 11,000 middle-aged people, having subclinical hyperthyroidism was associated with a 34% increased risk of subsequent fracture compared with those with euthyroidism during a median follow-up of 21 years (adjusted HR 1.34, CI of 95% 1.09-1.65), according to Stephen P. Juraschek, MD, PhD, of Beth Israel Deaconess Medical Center in Boston, and colleagues.

However, compared with those with normal thyrotropin and free thyroxine levels, fracture risk was not associated with subclinical hypothyroidism (aHR 0.90, 95% CI 0.77-1.05), the group reported. in Open JAMA Network.

The models were adjusted for various factors, including age, gender, race, diabetes status, menopausal status, body mass index, and vitamin D levels.

During the two decades of follow-up, a total of 3,556 new fractures (167.1 fractures per 10,000 person-years) were recorded. The rate of incident fractures per 10,000 person-years was:

  • 192.7 for those with subclinical hyperthyroidism
  • 180.8 for those with subclinical hypothyroidism
  • 165.8 for those with euthyroidism

The most frequent fracture locations were hip (14.1%) and spine (13.8%). Fracture-related hospitalizations were also much more common among those with thyrotropin levels below 0.56 mIU/L.

“Those with mildly suppressed thyrotropin levels (0.1 mIU/L to <0.56 mIU/L) might benefit from being identified as a high-risk group through more aggressive screening," the researchers suggested.

“It also supports the existing recommendation, which is to treat all patients aged 65 years and older with subclinical hyperthyroidism when the thyrotropin level is persistently less than 0.1 mIU/L for the prevention of bone mineral disease,” the researchers wrote. . They added that it “argues the potential need for tighter control of those with a thyrotropin level between 0.1 and 0.56 mIU/L to prevent bone resorption.”

While previous data has established the link between clinical hyperthyroidism and fracture through accelerated bone resorption without sufficient bone formation, Juraschek’s group noted that the new study also points to subclinical disease as a risk factor.

Data on these 10,946 adults (ages 45 to 64) were obtained from the ongoing Community Atherosclerosis Risk Study. Only those who self-identified as black or white were included.

Subclinical hyperthyroidism was defined as a thyrotropin level less than 0.56 mIU/L, subclinical hypothyroidism as a thyrotropin level greater than 5.1 mIU/L, and euthyroidism as a thyrotropin level of 0.56 to 5. 1mIU/L. All participants had normal free thyroxine levels of 0.85 to 1.4 ng/dL. Those taking any type of thyroid medication at the second follow-up visit were excluded.

Adults with subclinical hyperthyroidism were more likely to be black, have high blood pressure or diabetes, and be current smokers. On the other hand, people with subclinical hypothyroidism were more likely to be older women.

“Clinical trials are needed to elucidate the mechanisms by which subclinical thyroid dysfunction may be associated with fractures and other clinical outcomes,” the researchers noted.

  • Author['full_name']

    Kristen Monaco He is a staff writer, focusing on endocrinology, psychiatry, and nephrology news. Based in the New York City office, he has been with the company since 2015.

Disclosures

The Atherosclerosis Risk in Communities study was funded by the National Heart, Lung, and Blood Institute, NIH, and the US Department of Health and Human Services. Reagents for the thyroid assays were donated by Roche Diagnostics .

Juraschek and coauthors did not report relationships with industry.

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