IGF1 and sleep disorder: In a previous study, it was reported that sleep disorder caused a decrease in the weight and cross-sectional surface area of the tibialis anterior muscle in rats.6 In another study, it was shown that muscle regeneration is impaired and insulin-like growth factor 1 (IGF 1) levels is decreased in sleep disorder, and decreased IGF 1 levels can return to basal levels with the improvement of sleep.9 However, the number of histomorphological studies on this subject is limited.