THYROID AUTOANTIBODIES AND SOLUBLE INTERLEUKIN-2 RECEPTOR LEVELS IN PATIENTS WITH ACTIVE AND INACTIVE ACROMEGALY

Goiter is commonly associated with acromegaly, and patients with acrom egaly also have a significantly higher prevalence of Graves' disease a s compared with the general population. Excessive circulating levels o f growth hormone, growth factors, and cytokines may contribute to an a ltered immunological state predisposing to thyroid disease. Thirty acr omegalic patients (14 women and 16 men) were recruited for this study. Of 19 subjects with active acromegaly seven (36.8%) had an elevated t hyrotropin receptor antibody value (range: 26.6-54.0%, mean+/-SEM 37.8 +/-3.9). Four patients also had a positive anti-thyroperoxidase test ( range 75.4-180 U/ml). Three subjects (27.2%) with inactive acromegaly had a positive TRAb test (range 20-32%). Thyroid volume was larger in TRAb-positive patients (mean+/-SEM 55.2+/-9.4 ml) as compared with TRA b-negative subjects (19.1+/-1.9 ml, P < 0.001). Similarly, serum thyro globulin levels were significantly higher in TRAb-positive patients (m ean+/-SEM 47.8+/-6.7 mu g/l) as compared with TRAb-negative subjects ( 21.2+/-2.5 mu g/l, P < 0.001). Serum concentrations of soluble interle ukin-2 receptor (sIL-2R) were higher (mean+/-SEM 4407+/-527 pg/ml) in subjects with active acromegaly as compared with subjects with inactiv e disease (2670 +/-479 pg/ml). None of the patients in either group ha d an abnormally elevated thyroid hormone level. We concluded that acti ve acromegaly may elicit or induce an abnormal response of the immune system, with abnormally elevated levels of autoantibodies directed aga inst thyroid antigens appearing in about one third of the patients. Th e presence of elevated sIL-2R levels in some acromegalics may have an important role in this abnormal autoimmune response. Both findings may be connected to the higher prevalence of Graves' disease in acromegal ics.