Variations in somatomedin-C/insulin-like growth factor-I associated with environmental temperature and nutrition.

The influences of environmental temperature and energy intake on plasma concentrations of somatomedin-C/insulin-like growth factor-I (IGF-I) have been investigated in young growing pigs. After 10 weeks acclimation, IGF-I was significantly greater at 35 than 10 degrees C (P less than 0.001) and on a high than a low energy intake (P less than 0.001). During the period 16-26 h after the last meal, there was a significant decline in IGF-I with time (P less than 0.01). These results can be explained partly in relation to differences in energy exchange in warm and cold environments and may also be related to changes in growth and thyroid hormones.