The biological half-life of human growth hormone and a biologically active 20,000-dalton variant in mouse blood.

We compared the disappearance rate of hGH and hGH20K injected into groups of mice. Radioactivity measurements and RIA were used to determine the amount of hormone in blood collected at various times after injection. The results indicate that the T1/2 value for hGH and hGH20K are equal. We conclude that there is no apparent relationship between the equal rates of disappearance, the dissimilar binding characteristics that have been shown for the hormones and their equipotent growth promoting activities.