A synthetic 55-residue peptide consisting of the carboxyl portion of the predicted genomic DNA sequence of Shope fibroma virus growth factor (SFGF residue 26-80) was found to exhibit epidermal growth factor-transforming growth factor activities in newborn mice. The synthetic SFGF accelerated precocious incisor eruption and eyelid opening in newborn mice and also retarded the overall growth rates of hair, body weight and body length when administered in disages of 4 to 6 .mu.g per gram of body weight. The results of whole animal studies indicate that SFGF belongs to the EGF-TGF.alpha. family and exerts similar biologic effects in newborn animals.