Human growth hormone as usually isolated is a mixture of at least four different forms. Three are enzymically modified forms of hGH and the fourth is a disulfide dimer of the hormone. Chemical, biological and immunological characterization of the forms will be made. Enzymic digestion of hGH with a bacterial proteinase converted the hormone to a more active form. Complete characterization of the material is being made. The amino acid sequence of a number of growth hormones and prolactins is being made. The goal is to determine changes in structure that have occurred during evolution and how the biological activity is affected. The diabetogenic principle of the pituitary gland is being purified. Biological and chemical characterization will be carried out. BIBLIOGRAPHIC REFERENCES: Lewis, U.J.: Chemistry of Prolactin. Phar. Therap. 1, (1975). Singh, R.N.P., Seavey, B.K., Lewis, U.J. Heterogeneity of Human Growth Hormone. Endocrine Res. Comm. 1, 449 (1974).