In patients with subclinical hyperthyroidism, 27 excess fractures occurred per 10,000 person-years.

Overt hyperthyroidism confers risk for fractures due to uncompensated bone resorption. The relation between fracture risk and subclinical hyperthyroidism (defined as a normal free thyroxine level and a low thyroid-stimulating hormone [TSH] level) is less clear. In this prospective US study, researchers used a population-based sample of community dwelling people (mean age, 57 years) to compare 285 people with subclinical hyperthyroidism (mean TSH level, 0.4 mIU/L; in this lab, 0.56 mIU/L or higher was defined as normal) and 10,177 euthyroid people. People who took thyroid supplements were excluded.

During a median follow up of 21 years, 3556 fractures occurred: rates per 10,000 person-years were 193 in hyperthyroid patients and 166 in euthyroid people. The hazard ratio, adjusted for a wide range of clinical factors associated with bone loss, was 1.34 for hyperthyroid versus euthyroid patients.

Comment: This study extends previous findings suggesting that subclinical hyperthyroidism is a risk factor for fractures. American Thyroid Association guidelines recommend treatment for subclinical hyperthyroidism when TSH level is below 0.1 mIU/L in older patients (age 65 years or older) and in younger patients with comorbidities; for people in these risk groups whose TSH level is between 0.1 mIU/L and 0.4 mIU/L, the guideline recommends only that clinicians ‘consider treating’ (Thyroid 2016; 26: 1343-1421).

THOMAS L. SCHWENK, MD
Professor Emeritus, Family and Community Medicine, University of Nevada School of Medicine, Reno, USA.

Daya NR, et al. Association between subclinical thyroid dysfunction and fracture risk. JAMA Netw Open 2022; 5: e2240823.

This summary is taken from the following Journal Watch title: Hospital Medicine