The endogenous digitalis-like compounds (DLC)are steroid hormones synthesized and released from the adrenal gland.They are integrated in the feed-back system of the Hypothalami-Pituitary-Adrenal gland axis.One of their remarkable function is to induce apoptosis in malignant cells. Recently, accumulating data point to the possibility of using synthetic DLC as new anti-cancer drugs. Less is known about the endogenous metabolism of these compounds in cancer patients. Proceeding from preliminary clinical data which demonstrated significantly reduced DLC plasma levels in breast cancer patients and from in vitro data which showed an impaired release of DLC towards stress stimuli in athymic nude mice,we put up the hypothesis that a latent adrenal insufficiency with low DLC levels facilitates the induction and progression of tumor diseases.