Immunoreactive endothelin in nodular pathology of the thyroid.

ABSTRACT

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 degrees C until assayed. Sera were frozen at -20 degrees 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 degrees 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.