Mechanisms of glucocorticoid inhibition of growth.

Mechanisms whereby glucocorticoids might inhibit growth are reviewed from the perspective of glucocorticoid effects on cell metabolism and growth. Although glucocorticoids given to patients decrease levels of growth hormone and possible somatomedins, the effect of glucocorticoids on growth is not reversed when growth hormone is given. Glucocorticoids inhibit cell growth in culture. Cell inhibition correlates with binding of steroids to the glucocorticoid receptors. Some tissues are very sensitive; others are insensitive. In cell culture, changes in sensitivity can be associated with changes in binding, but this is not always the case in tissues of the animal. The mechanisms of inhibition of cell growth are not known. It could be due to steroid-induced synthesis of inhibitory proteins or to blocking by receptor-steroid complexes of the synthesis of RNA. Steroids may affect uptake of substrates, e.g., glucose or amino acids, which in turn affects growth. The inhibitory actions of glucocorticoids on individual tissues may explain why these steroids inhibit growth in the animal. It is not known, however, how the steroid inhibits linear growth in mass or which cell types are most important targets for such effects.