Somatropin 4 I.U. is a form of recombinant human growth hormone (HGH) used to treat growth hormone deficiency in children and adults. It works by replacing the deficient natural growth hormone, promoting growth, increasing muscle mass, improving bone density, and enhancing metabolism and nutrient absorption. Somatropin is administered by injection under the skin and is prescribed for conditions like growth failure, short stature, and certain other medical disorders related to insufficient growth hormone production. It is a synthetic version of the natural hormone produced by the pituitary gland and helps regulate various metabolic processes and growth functions in the body.