Immunoreactive endothelin in nodular pathology of the thyroid

OBJECTIVES Endothelins (ETs) can act as autocrine and/or paracrine regulators of thyroid homeostasis and growth. The aim of this study was to evaluate immunoreactive ET (i‐ET) levels in a group of patients with nodular pathology of the thyroid and to correlate them with the cytomorphological features after fine‐needle aspiration (FNA) and with hormonal and immunological status and blood pressure levels. DESIGN Plasma and cystic i‐ET were assayed in a group of patients with varying thyroid function, who underwent FNA for solid and cystic nodular pathology. PATIENTS 47 patients (32–81 years) with nodular pathology of the thyroid and 18 controls (28–70 years) with normal thyroid function and morphology were studied. MEASUREMENTS Fasting venous blood samples were collected and the plasma for i‐ET was frozen at −80°C until assayed. Sera were frozen at −20°C for FT3, FT4, TSH, TPO autoantibodies and thyroglobulin autoantibodies assay. Cystic fluid was obtained by FNA, centrifuged, and the supernatant was stored at −20°C until i‐ET assay. FNA cytology was examined by light microscopy. RESULTS In patients with cystic nodules, plasma i‐ET levels were significantly (P = 0.002) higher (5.7 ± 1.1 ng/l, ± SEM) than in both patients with solid nodules (2.6 ± 0.4 ng/l) and (P = 0.02) controls (3.0 ± 0.3 ng/l). In patients with cystic nodules, cystic i‐ET levels (12.6 ± 1.9 ng/l) were significantly (P = 0.003) higher than plasma levels (5.7 ± 1.1 ng/l) and did not correlate with the percentage of FNA cellularity. i‐ET levels in cystic fluid (12.6 ± 1.9 ng/l) were significantly (P = 0.0001) higher than plasma i‐ET levels in both patients with solid nodules and controls. No difference in either plasma or cystic i‐ET levels was found in patients with cystic nodules in relation to differences in thyroid function. No difference in plasma i‐ET levels was found between patients with solid nodules and controls. In controls, no significant difference in plasma i‐ET levels was found between males and females. A negative correlation (r = −0.55, P = 0.02) was found between cystic i‐ET levels and systolic and diastolic blood pressure. No correlation between cystic or plasma i‐ET levels and FT3, FT4 or TSH was found in any of the subjects studied. CONCLUSIONS It seems that endothelins do not possess a primary role in determining thyroid function and that the increased levels in cystic fluid found in our subjects could be secondary to cystic nodule development.