Increased plasma endothelin level as an endothelial marker of cardiovascular risk in patients with active acromegaly: a comparison with plasma homocysteine.

The aim of the present study was to evaluate the plasma endothelin-1 (ET-1) and total homocysteine (tHcy) levels as biochemical markers of endothelial dysfunction and atherosclerosis in patients with active and cured acromegaly in order to assess the relationship between the secretory status of growth hormone (GH)/insulin-like growth factor I (IGF-I) and ET-1/tHcy levels. The patients were divided in two subgroups: 1) patients with active disease (n = 30); and 2) patients with nonactive cured acromegaly (n = 21). Plasma ET-1 levels were directly determined by a highly sensitive enzyme immunoassay and plasma tHcy concentrations were measured by a fluorescence polarization immunoassay. In active acromegaly subjects, plasma ET-1 levels were 1.24 +/- 0.2 pmol/L, significantly higher than in both nonactive acromegalics (0.39 +/- 0.1 pmol/L) and age-matched healthy controls (0.49 +/- 0.2 pmol/L) (P < 0.001). Plasma tHcy concentrations, however, did not differ significantly in all studied groups: nonactive acromegalics: 9.54 +/- 4.42 micromol/L; active acromegalics: 9.0 +/- 3.14 micromol/L; and control subjects: 9.96 +/- 2.95 micromol/L (P > 0.05). In conclusion, our study demonstrated that elevated ET-1 levels probably contributed to premature atherosclerosis and cardiovascular disease and represent a new risk factor for endothelial dysfunction and early vascular complications in acromegaly. We propose that GH and IGF-I secretory status are important determinants of plasma ET-1 but not tHcy levels.