DIURNAL RHYTHM OF SERUM ERYTHROPOIETIN CIRCULATING LEVELS IN CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

Objective. Since erythropoietin (Epo) presents a diurnal rhythm in its circulating serum levels and it is reported increased in patients wit h chronic obstructive pulmonary disease (COPD), the circadian rhythm o f Epo was investigated in a group of 40 normocytemic patients with chr onic obstructive pulmonary disease compared with 40 clinically healthy subjects. Methods. Venous blood samples were drawn in each subject du ring the span of a whole day every four hours, starting from midnight, for the determination of serum Epo levels by RIA. Statistical analysi s was carried out by chronograms and by means of the ''cosinor'' metho d. Results. The control group presents a significant (p<0.001) circadi an rhythm in serum Epo levels, with maximum in the afternoon, whereas no rhythm (p>0.05) is detected in the patient group. This has signific antly (p<0.05) higher mean daily levels and lower diurnal variations o f serum Epo than the control group; a significant (p<0.05) difference exists between the two groups regarding the peaks of rhythms. Conclusi on. These data confirm the presence of circadian rhythm in serum Epo l evels and suggest that the COPD, by daytime hypoxemia with associated severe nocturnal desaturation, is associated with increased serum Epo levels both by day and by night, so that the physiological circadian r hythm is lost in these patients.