The 20,000-dalton structural variant of human growth hormone: Lack of some early insulin-like effects

In contrast to the major form of human growth hormone the 20,000-dalton (20K) variant of the hormone produced no decrease in either serum glucose of free fatty acids one hour after injection into fasted, hypophysectomized rats. Furthermore, the variant caused no rise in serum free fatty acids after 5 hours. In vitro experiments utilizing epididymal adipose tissue from hypophysectomized rats indicated that 20K was unable to accelerate glucose utilization as measured by glucose uptake and CO 2 formation. The data show that this form, even though growth promoting, lacks some of the metabolic properties attributed to growth hormone. We conclude that an insulin-like effect is not necessarily a prerequisite for growth promoting activity.