Firstly, unlike short stature or growth retardation, which could sometimes be non-specific due to decrease in overall organismal fitness, overgrowth syndrome tend to be more specific about growth, and especially if it was not caused by increase in growth hormone or insulin-like growth factor I (IGF-I), could point to new biology about bone growth; and secondly, such connection between overgrowth and epigenetic regulators may imply that epigenetic modifications are involved in limitation of overall organismal body size, which has been a fascinating mystery in biology (34). Here, IGF1 is linked to overgrowth syndrome.