Patients with subclinical hyperthyroidism are at higher risk of experiencing a fracture compared to those who are euthyroid or have subclinical hypothyroidism, suggests a recent study published in the journal JAMA Network Open.¹

Participants from the ongoing Atherosclerosis Risk in Communities Study were enrolled for this study. More than half (54.3%) of the study subjects were women. Through this study, the researchers aimed to discover an association between subclinical thyroid dysfunction and risk of fracture. TSH level <0.56 mIU/L was defined as subclinical hyperthyroidism for the study; TSH level >5.1 mIU/L was considered as subclinical hypothyroidism, while TSH levels ranging between 0.56 mIU/L and 5.1 mIU/L and T4 level from 0.85-1.4 ng/dL were categorized as euthyroid.

In this study of 10,946 participants, 93% were euthyroid, 4.4% had subclinical hypothyroidism, while 2.6% were found to have subclinical hyperthyroidism. A total of 3556 new fractures (167.1 per 10,000 person-years) occurred during the follow up period of 21 years (median). Compared to euthyroid patients, the risk of fracture was increased by 34% among those with subclinical hyperthyroidism with an adjusted hazard ratio of 1.34. However, when patients with subclinical hypothyroidism were assessed, their risk of fracture was comparable to the euthyroid participants (aHR 0.9). Patients with normal T4 levels and TSH levels in the lower-than-normal range were much more likely to require hospital admission because of the fracture. Individuals with TSH levels less than 0.56 mIU/L had a higher fracture risk.

Based on their findings, the authors suggest subclinical hyperthyroidism as a risk factor for fracture. Hence, these patients should be regularly examined during follow-up visits to prevent bone mineral disease.

Reference

1. Daya NR, et al. Association between subclinical thyroid dysfunction and fracture risk. JAMA Netw Open. 2022 Nov 1;5(11):e2240823. doi: 10.1001/jamanetworkopen.2022.40823.