INSULIN-LIKE GROWTH FACTOR-I AND GROWTH-HORMONE IN CANINE STARVATION

The roles of plasma insulin-like growth factor I (IGF I) and growth hormone (GH) were studied in 7 beagle dogs before and during starvation and during refeeding. IGF I levels significantly decreased from 75.2 .+-. 5.9 ng/ml at 7 days prior to the start of starvation to 9 .+-. 1.7 ng/ml at 19 days after the commencement of starvation (mean .+-. SEM [standard error of the mean]; P < 0.0001). During refeeding IGF I significantly rose from 9 .+-. 1.7 ng/ml to 55.5 .+-. 7.5 ng/ml within 9 days (mean .+-. SEM; P < 0.002). During starvation plasma GH levels significantly increased (P < 0.05) and these elevated levels returned to normal during refeeding. The dogs'' GH secretory capacity significantly increased during starvation (P = 0.012) and became normal again during refeeding. Starvation in the dog leads to a significant and drastic reduction of the circulating levels of IGF I. Starvation in the dog, as in man, leads to increased circulating GH levels and to an increased GH-secretory capacity possibly brought about by a lack of a negative feedback normally exerted by IGF I.