In order to examine the imbalanced hormone circuit caused by uremia, the serum level of human growth hormone (STH), insulin-like growth factor 1 (IGF 1), insulin and prolactin of 34 renal failure sufferers have been determined before and during the dialysis therapy. 21 patients were treated by using hemo dialysis, whereas 13 patients underwent peritoneal dialysis. Limited to peritoneal dialysis patients, the hormone level of peritoneal dialysate has been measured additionally. STH, a polypeptide with a molecular weight (MW) of 21,900 daltons, acts anabolically, lipolytically, carbohydrate-saving and growth accelerating. Usually, those effects are mostly transmitted by means of other factors, e.g. IGF-1. The latter, another polypeptide with a MW of 7,650 daltons, acts as a mitogen and is involved in the cell development process in almost all types of tissue. Insulin, a polypeptide with a MW of 7,650 daltons, enhances the intake of glucose in liver and muscle cells as well as in adipose tissue. Insulin is the only consequently anabolically acting hormone. Prolactin, another polypeptide with a MW of 26,363 daltons, has, as far as it can be said today, only a function in the process of lactation. However, recent studies also deal with the role of prolactin in cell proliferation. Changes in the basal level during renal failure (i.e. increased STH, IGF-1 normal or slightly increased, insulin normal or increased, prolactin increased) as described in previous publications could be confirmed except for the STH level. Findings regarding STH delivered normal values, except for female peritoneal dialysis patients with results that were not significant. Instead of that, this group showed an increased level before and during the first two quarters of the dialysis therapy. Results measured during the dialysis therapy did not diverge from findings published so far. During the therapy, no significant changes in serum concentrations could be found except for the group of female peritoneal dialysis patients. When comparing the type of dialysis, STH-, IGF-1 and prolactin levels were significantly increased in peritoneal dialysis patients. The analysis of hormone elimination rates in dialysate during peritoneal dialysis showed significantly higher IGF-1, insulin and prolactin levels and significantly decreased STH levels in female patients in contradiction to male patients. The loss of hormones in peritoneal dialysate depends on the molecular size of hormones and their adhesion with transport proteins. Correlational research between serum levels of hormones produced contradictory results, hence requiring further investigation.