Insulin and growth hormone: regulators of growth with particular reference to muscle

Abstract

The growth-regulating property of GH operates mostly by its capacity for stimulating cell replication. Where there is a deficiency of GH or when tissue response to GH is reduced (calorie deficiency) the effect is a diminution in cell number. In some of these instances, an overreponse to insulin leads to an increase in cell size (a higher protein:DNA ratio). Insulin, in contrast, exercises its growth-promoting effects by its ability to stimulate protein synthesis and depress protein degradation; its effect is to stimulate growth in cell size. Growth in cell size is retarded where insulin deficiency exists. Imbalance in either hormone not only interferes directly with growth of cells but also triggers other hormonal imbalances, e.g., somatomedin. Growth retardation in uremia has some of its base in undernutrition, which can be mediated through changes in hormonal balance. Uremia may directly effect tissue response to hormone as in the case of insulin. Future investigations of growth retardation in kidney disease may find hormone imbalance as a potential cause for growth inhibition. It can be pointed out further that children with a diminished nephron population are in a position where each nephron is acting to a maximal extent to clear waste products of metabolism. With further growth and an increase in the number and size of cells, the load on the kidney will increase.