Glucocorticoids make standard part of many therapeutic regimens used in treating lymphoproliferative diseases. Their administration is performed within the framework of a specific chemotherapy cycle, usually in a series of pulses lasting several days, when a patient is exposed to many times higher glucocorticoid levels than is their average daily production. In this situation the development of a serious functional lesion in hormone axis indicated as adrenocortical insufficiency with its typical manifestations seen after the corticoid therapy interruption, including muscular weakness, fatigue, loss of weight and anorexia, can take place. The case report given here describes the case of a man with multiple myeloma showing after several chemotherapeutical cycles with dexamethasone and bortezomib a set of inconsistent symptoms which are dominated by hypersomnia, autonomic movements in sleep and weight growth. After many medical examinations, including cerebral CT, lumbar puncture and examination in a sleep laboratory, the disorder was diagnostically closed as hypopituitarism with impaired adrenocorticotropic and gonadotropic axes, including growth hormone deficit. Furthermore, a surprising finding was also made, namely that the original predominant clinical symptomatology in the form of excessive sleepiness had not been sleep at all and, apparently, manifestation of extreme fatigue in deep hypocortisolism had been the case. The patient has been given corticoid replacement therapy and, based on the results blood exams, after approximately half a year of such therapy gradual restitution of the hypothalamus-pituitary-adrenal axis is quite apparent.