An intracellular signaling molecule with protein kinase activity known as Akt1 (a major isoform of Akt) [ 6 ] may play a central role in the atrophic and hypertrophic responses of muscle to glucocorticoids and IGF-I, respectively [ 7,8 ]. Glucocorticoid-induced suppression of Akt1 ultimately results in increased amounts of the ubiquitin-ligase atrogin-1 (MAFbx) that targets muscle proteins for degradation [ 7,9 ]. Conversely, IGF-I signaling leads to enhanced activity of Akt1 that suppresses muscle atrophy and that induces muscle hypertrophy [ 8 ].
Pregnancy Category C. Corticosteroids have been shown to be teratogenic in many species when given in doses equivalent to the human dose. Animal studies in which corticosteroids have been given to pregnant mice, rats, and rabbits have yielded an increased incidence of cleft palate in the offspring. There are no adequate and well-controlled studies in pregnant women. Corticosteroids should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Infants born to mothers who have received corticosteroids during pregnancy should be carefully observed for signs of hypoadrenalism.