Nevertheless, these observations suggested that handgrip strength is associated with multiple physiological systems and the mechanisms underlying handgrip strength deterioration, such as insulin resistance, hyperthyroidism (Harrison and Clausen 1998; Wang et al. 2006), increased interleukin-6 or reduced insulin-like growth factor I (IGF-I) (Barbieri et al. 2003), are common to other diseases. Here, IGF1 is linked to hyperthyroidism.