Parathyroid hormone is inversely related to endothelin-1 in patients on haemodialysis

Aim: Parathyroid hormone secretion is mainly influenced by hypocalcaemia, hyperphosphataemia and vitamin D deficiency. However, previous in vitro and in vivo studies showed that endothelin-1 can influence parathyroid hormone secretion. This study was aimed at evaluating this relationship in vivo in uraemic patients. Methods: Parathyroid hormone and endothelin-1 plasma concentrations were measured in 67 haemodialysed patients. Patients with history of cardiovascular diseases and those with parathyroid adenoma were excluded. Results: Plasma levels of endothelin-1 were found to be inversely related to those of parathyroid hormone (P < 0.04) The multiple regression analysis, carried out considering parathyroid hormone as a dependent variable, and including age, sex, blood pressure, calcium ¥ phosphorus product, and endothelin-1, demonstrated that the independent correlates of parathyroid hormone were endothelin-1 (b = -0.276; P = 0.015), and calcium ¥ phosphorus product (b = 0.417; P < 0.0001). Conclusion: For the first time in vivo, we demonstrated an inverse independent relationship between endothelin-1 and parathyroid hormone in haemodialysed patients. Because both endothelin-1 and parathyroid hormone are endowed with well-known harmful actions on cardiovascular apparatus, whether such inverse relation may really influence the natural history of cardiovascular damage due to secondary hyperparathyroidism remains to be elucidated.