The Fracture Risk Assessment Tool (FRAX score) in subclinical hyperthyroidism

The Fracture Risk Assessment Tool (FRAX score) is the 10-year estimated risk calculation tool for bone fracture that includes clinical data and hip bone mineral density measured by dual-energy x-ray absorptiometry (DXA). The aim of this cross-sectional study was to elucidate the ability of the FRAX score in discriminating between bone fracture positive and negative pre- and postmenopausal women with subclinical hyperthyroidism.

The bone mineral density (by DXA), thyroid stimulating hormone (TSH) level, free thyroxine (fT4) level, thyroid peroxidase antibodies (TPOAb) titre, osteocalcin and beta-cross-laps were measured in 27 pre- and postmenopausal women with newly discovered subclinical hyperthyroidism [age 58.85 +/- 7.83 years, body mass index (BMI) 27.89 +/- 3.46 kg/m2, menopause onset in 46.88 +/- 10.21 years] and 51 matched euthyroid controls (age 59.69 +/- 5.72 years, BMI 27.68 +/- 4.66 kg/m2, menopause onset in 48.53 +/- 4.58 years). The etiology of subclinical hyperthyroisims was autoimmune thyroid disease or toxic goiter. FRAX score calculation was performed in both groups.

In the group with subclinical hyperthyroidism the main FRAX score was significantly higher than in the controls (6.50 +/- 1.58 vs. 4.35 +/- 1.56 respectively; p = 0.015). The FRAX score for hip was also higher in the evaluated group than in the controls (1.33 +/- 3.92 vs. 0.50 +/- 0.46 respectively; p = 0.022). There was no correlations between low TSH and fracture risk (P > 0.05). The ability of the FRAX score in discriminating between bone fracture positive and negative pre- and postmenopausal female subjects (p < 0.001) is presented by the area under the curve (AUC) plotted via ROC analysis. The determined FRAX score cut-off value by this analysis was 6%, with estimated sensitivity and specificity of 95% and 75.9%, respectively.

Pre- and postmenopausal women with subclinical hyperthyroidism have higher FRAX scores and thus greater risk for low-trauma hip fracture than euthyroid premenopausal women. Our results point to the use of FRAX calculator in monitoring pre- and postmenopausal women with subclinical hyperthyroidism to detect subjects with high fracture risk in order to prevent further fractures.