Incidence of pituitary autoantibodies in idiopathic diabetes insipidus

Diabetes insipidus is a disorder resulting from insufficient action of vasopressin (ADH) characterized by excretion of highly diluted urine in large amounts. Idiopathic diabetes insipidus is associated with the presence of both autoantibodies against ADH-secreting neurons and pituitary autoantibodies. The aim of the present study was to evaluate the occurrence of autoantibodies against the pituitary microsomal fraction. The study included 33 sera of diabetes insipidus patients and 10 control sera obtained from 10 healthy persons. In all patients the secretion of pituitary hormones and thyroid autoantibodies was assessed. Human pituitaries were obtained during autopsy and homogenized in 0.01 mol/l pH 7.4 phosphate buffer. In addition, for the autoantibody evaluation, the electrophoretic method of separation in polyacrylamide gel and western blot were employed. Among the 33 subjects, in 23 patients the presence of autoantibodies against the pituitary was shown. Sera of 15 patients reacted with the pituitary microsomal fraction protein of 55 kDa. In other cases, 10 sera reacted with the pituitary antigen of 67 kDa. In addition, 5 sera reacted with the 60 kDa antigen, 5 sera with 52 kDa protein, 3 sera with 105 kDa protein, 3 sera with the 97 kDa antigen and 2 sera with pituitary antigen of 92 kDa weight. In our study, based on the immunoblotting method, we observed that pituitary autoantibodies against 55, 60 and 67 kDa antigens occurred frequently.