Abstract
1. Betamethasone caused growth retardation, adrenal atrophy and impaired hypothalamo-pituitary-adrenal (HPA) activity in the rat.2. In spite of the profound impairment, recovery of normal HPA function was rapid, but the growth retardation persisted.3. The ability of the pituitary gland to secrete basal corticotrophin (ACTH), recovered more rapidly and the adrenocorticotrophic response to stress less rapidly than the ability of the adrenal cortex to respond to ACTH.4. The degree of HPA suppression was not determined by the total dose of steroid.5. The possible significance of the results is discussed.