CIRCADIAN-RHYTHM OF SERUM ERYTHROPOIETIN IN MULTIPLE-MYELOMA

The diurnal rhythm in the circulating serum levels of erythropoietin ( EPO) were determined in a group of 20 adult clinically-healthy subject s, in a group of 10 patients with myeloma without renal impairment and 10 patients with myeloma and renal failure, Venous blood samples were drawn during the span of a whole day and every 4 hr, starting from mi dnight, for the measurement of serum EPO levels by radioimmunoassay (R IA), Statistical analysis was carried out by means of the ''cosinor'' method. Results show that the controls and the myeloma patients withou t renal insufficiency present significant (P < 0.05) circadian rhythms in serum EPO levels; no rhythm (P < 0.05) was detected in patients wi th myeloma and renal failure, Patients with myeloma and renal failure have significant (P < 0.05) lower mean daily levels and diurnal fluctu ations of EPO than the other groups, whereas the patients with myeloma without renal involvement present higher (P < 0.05) mean daily levels and lower (Pi 0.05) diurnal variations of EPO than controls; no diffe rences (P > 0.05) exist between the groups regarding peaks of rhythms, These data confirm the existence of a physiological circadian rhythm in serum EPO concentrations, with maximum in the afternoon, and they s uggest that renal failure is an important cause of anemia and loss of EPO circadian rhythm in patients with myeloma. (C) 1996 Wiley-Liss, In c.