Long-term effects of recombinant human erythropoietin therapy on growth hormone secretion in uremic patients...

Recombinant human erythropoietin (rhEPO) is being successfully used for the treatment of uremic anemia. Short-term studies have proved that correction of anemia with rhEPO therapy is accompanied by several changes in growth hormone (GH) secretion in uremic patients. The present study aimed to assess the influence of long-term rhEPO therapy on baseline and stimulated GH concentrations in a group of uremic patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Seven well-nourished and clinically stable CAPD patients were studied. Ten normal subjects were studied as controls. GH responses to direct pituitary stimulation with GH-releasing hormone (GHRH) (100 microg intravenously [i.v.]) and indirect hypothalamic stimulation with insulin-induced hypoglycemia (0.1 U/kg body weight i.v.) and clonidine (0.15 mg/m2 orally), were assessed before and after 3, 6, and 12 months of subcutaneously administered rhEPO therapy. After rhEPO administration, an increase of the hemoglobin concentration was observed in all patients and maintained at about 12 g/dL throughout the study period. rhEPO therapy did not induce any significant change in baseline concentrations of GH and insulin-like growth factor I. Correction of the anemia was accompanied by a clear increase in the area under the curve (AUC) and the area above the baseline (AAB) of GH secretion in response to GHRH stimulation. These changes were statistically significant after 3 and 6 months of therapy, although at 12 months no significant differences in relation to pretreatment values could be observed. rhEPO treatment was associated with a progressive decrement in the GH AUC and AAB in response to hypoglycemic challenge, reaching statistically significant values at months 6 and 12. On the other hand, compared with the control group, GH responses to clonidine were blunted at the start of the study in CAPD patients, and rhEPO therapy was not accompanied by any modification. In conclusion, long-term treatment with rhEPO in CAPD patients is associated with complex and profound effects on somatotrope cell function, characterized by diverse effects on GH responses to stimuli that release GH through different mechanisms. Some of these rhEPO-induced alterations in somatotrope function are dependent on the duration of treatment.