The rationale for the use of recombinant human growth hormone and insulin-like growth factor-I for catabolic conditions in humans

Patients with a variety of catabolic illnesses or conditions are subjected to protein catabolic losses which we attempt to address with traditional enteral or parenteral nutritional support. Accelerated protein catabolism and energy requirements together with inadequate intake or assimilation of exogenous amino acids are all contributing causes. Circulating glucocorticosteroids may play a significant contributing role in the redistribution and loss of body protein in acute, and possibly chronic, catabolic illnesses but such complex metabolic conditions are not easily studied. Short-term, high-dose glucocorticosteroid administration, a model for such protein catabolic condition, increases rates of whole-body proteolysis, increase amino acid oxidation, and decrease the effectiveness insulin in suppressing proteolysis. Recombinant human growth hormone (rhGH) administration alone in humans decreases amino acid oxidation and increases the estimated rate of whole body protein synthesis. The exact proteins affected by rhGH and the nutritional implications of this, remain to be determined. rhGH when given in combination with high-dose glucocorticosteroids offsets the protein catabolic effects of steroids alone. Thus, rhGH might provide a means to manipulate protein homeostasis in acute and possibly chronic catabolic conditions. Current data with the use of IGF-I is less clear and will require further investigation to clarify its potential role in such conditions. Finally, clear clinical utility of adjunctive rhGH and/or rhIGF-I therapy must be demonstrated to justify its wide applicability in specific clinical settings as a standard care.