*4.1.2. Overt hypothyroidism and skeletal changes*

Large population based studies identified an increased fracture risk in individuals with hypothyroidism (Vestegaard et al 2000; 2002). The first of these studies (Vestegaard et al, 2000) analyzed 408 patients with primary hypothyroidism and found a temporary increase in fracture risk within the first 2 years after diagnosis, mainly in the age group >50 years, and was limited to the forearms. In the following study (Vestegaard, 2002), 4473 patients with autoimmune hypothyroidism (mean age, 66.1 +/- 17.3) were shown to present a significantly increased fracture risk up to 8 years prior to diagnosis with a peak around the time of diagnosis. The fracture risk was found to return to normal more than 5 years after its diagnosis.

An increased fracture risk in hypothyroid patients is not probably due to modifications of bone density. There are no convincing literature data as to changes in bone architecture during hypothyroidism. Neuromuscular symptoms and impaired muscle energy metabolism could be responsible for bone changes in this population. Hypothyroid patients have been shown to display impaired neuromuscular response to exercise persisting even after restoration of euthyroid status (Caraccio et al, 2005).
