Disclosures: The authors report no relevant financial disclosures.
December 28, 2020
3 min read

BMD, bone microarchitecture improve in women after euthyroid restoration

Disclosures: The authors report no relevant financial disclosures.
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Women with hyperthyroidism had improvements in bone mineral density and bone microarchitecture 1 year after attaining euthyroid status, according to findings published in Thyroid.

“Hyperthyroid women were found to have compromised cortical microarchitecture, lower volumetric BMD and lower estimated bone strength in the radius compared with the healthy control subjects, while the tibia was not significantly affected,” Thomas Heiberg Brix, MD, PhD, department of endocrinology at Odense University Hospital in Denmark, and colleagues wrote. “After 1 year of euthyroidism, significant improvements in volumetric BMD and cortical microarchitecture were observed. These results seem to reflect an inappropriate bone remodeling in hyperthyroidism, inflicting an improper bone microarchitecture.”

Thyroid anatomy 2019
Source: Adobe Stock

Lower BMD, bone strength with hyperthyroidism

Brix and colleagues conducted two studies at an endocrine outpatient clinic at Odense University Hospital from May 2011 to January 2016. The first was a case-control study in which 61 women aged 20 to 85 years with newly diagnosed overt or mild hyperthyroidism due to Graves’ disease or toxic nodular goiter were enrolled. High-resolution peripheral quantitative CT of the distal radius and tibia, and DXA of the lumbar spine and hip were performed, and fasting blood samples were drawn. The hyperthyroid participants were matched by age, sex and menopause status with a healthy control group randomly selected from the general population. Control participants took part in a study examining age- and sex-related changes in bone microarchitecture in adults. The control cohort was examined using the same equipment and similar setup as the hyperthyroid group.

In analysis of the high-resolution peripheral quantitative CT of the radius, the hyperthyroid group had 16.9% more total area, 28.6% more trabecular area and 11.7% less lower cortical area than the control cohort (P < .001 for all). There was also a lower mean volumetric BMD (13.9%; P < .001), cortical volumetric BMD (5.8%; P < .001), cortical thickness (16.7%; P < .001) and estimated bone strength (6.6%; P < .01) in the hyperthyroid group compared with controls. No differences were found in the tibia. DXA showed no differences in the hip or spine.

Restored bone microarchitecture with euthyroidism

Researchers conducted a follow-up study of 46 hyperthyroid participants from the first study. Participants were treated with antithyroid drugs, thyroidectomy or radioiodine according to routine care, and thyroid function tests were performed every 4 to 8 weeks until euthyroid restoration. Twelve months after restoration, participants were reexamined with both bone scans and blood samples. The follow-up data were compared with data collected during the first study.

At follow-up, the study population had a 2.1% mean increase in cortical area and a 0.5% decrease in the trabecular area of the radius (P < .01 for both). There was also a 0.8% mean increase in total volumetric BMD (P < .05), a 2.5% increase in cortical thickness (P < .01) and a 2% increase in trabecular separation (P < .05).

In the tibia, the group had a 3.6% mean increase in cortical area, a 0.5% decrease in trabecular area and a 3.8% increase in cortical thickness (P < .01 for all). DXA scans showed areal BMD increased in the spine by 1.1% (P < .05) and in the hip by 2% (P < .01).

The study population was divided into a low 25-hydroxyvitamin D group (n = 23; < 67.6 nmol/L) and a high 25-(OH)D cohort (n = 23; > 67.6 nmol/L). No differences were seen between the two groups in the first study. At follow-up, high-resolution peripheral quantitative CT parameters showed more positive changes in the low group vs. the high group, particularly in the radius. Changes in 25-(OH)D level did not alter findings in the bone parameters.

“We show that hyperthyroidism has negative impact on bone microarchitecture, primarily in the radius, but with improvement following treatment,” the researchers wrote. “Whether high-resolution peripheral quantitative CT parameters have any predictive value in relation to the fracture risk in hyperthyroid patients remains to be elucidated in larger scale and longer-term follow-up studies.”