The hidden but positive role for glucocorticoids in the regulation of growth hormone-producing cells

Growth hormone (GH) is a prominent metabolic factor that is targeted by glucocorticoids; however, their role in GH production remains controversial. This is explained in part by discrepancies between in vitro and in vivo, short-term versus long-term exposure and even species-specific effects. The prevailing view, however, is that glucocorticoids are negative modulators of growth and GH production. An examination of recent findings from elegant avian and gene ablation in mice studies as well as clinical case reports, suggests this is not the case. The evidence suggests that the effect of glucocorticoids on growth and GH production can be uncoupled, and reveals they play a crucial and positive role in maturation of functional somatotrophs, the GH-producing cells of the anterior pituitary. Here, we provide an overview and insights into the possible roles of glucocorticoids in the development of somatotrophs before birth as well as regulation of GH production in infancy (neonatal) and adulthood (postnatal). A fully functional glucocorticoid-signaling pathway appears to be required for establishment of somatotrophs before birth, and glucocorticoids continue to be required for maintenance of GH production in the newborn. There is evidence to suggest progenitor somatotrophs may persist after birth, and perhaps account for the ability of glucocorticoid therapy to correct some cases of GH deficiency as a result of compromised glucocorticoid signaling. Finally, there is support for positive regulation of avian, murine and human GH gene activation and/or expression by glucocorticoids, however, there appears to be no common mechanism and the contribution of direct versus indirect effects remains unclear. Thus, our observations reveal a largely hidden face of glucocorticoids, specifically, a positive role in somatotroph development and GH gene activation/expression, which may enable us to better understand the differential effect of glucocorticoids on growth and GH production in human studies.