Aim: To study fracture risk and risk factors for fractures in patients with primary idiopathic hypothyroidism (ICD 10: E03.9).
Design: Historical follow-up.
Material and methods: A self-administered questionnaire was issued to 628 patients with primary idiopathic levothyroxine-substituted hypothyroidism. A total of 412 (65.6%) responded and of these, 408 could be analyzed. The 408 respondents were age- (+/- 5 years) and gender-matched with 408 normal controls randomly selected from the background population who responded to the same questionnaire.
Results: Overall fracture risk was increased in patients compared to controls (relative risk: RR = 1.6, 95% CI: 1.0-2.5). However, the increase was temporary and limited to the period within the first 2 years after the diagnosis of hypothyroidism (RR = 3.1, 95% CI: 1.4-7.0). Before the diagnosis and more than 2 years after the diagnosis, the fracture risk in patients did not deviate from that of the controls. The increase in fracture risk was only significant in the age group above 50 years (RR = 1.8, 95% CI: 1-3.2), and was limited to the forearms (RR = 3.0, 95% CI: 1.4-6.3 for the entire patient population).
Conclusions: There was a temporary increase in fracture risk within the first 2 years after diagnosis of primary idiopathic hypothyroidism. The fracture risk was mainly increased in the age group above 50 years, and the increased risk was limited to the forearms.