Abstract
9alphaFluorohydrocortisone, prednisolone, and hydrocortisone promoted the growth of the human tumour (H.S.l) in weanling rats, but deoxycortone acetate was ineffective even when injected in very high dosage; Cortrophin ZN, a long-acting corticotrophin preparation, was just as effective as cortisone. This effect of corticotrophin on tumour growth was mediated by the adrenal cortex, and was related to the enhanced secretion of adrenocorticoids; some correlation existed between tumour size and adrenal hypertrophy in the corticotrophin-treated rats. The action of adrenal steroids and of corticotrophin in promoting the growth of the tumour is discussed.