[Detection of pituitary autoantibody in patients with pituitary tumors and hypopituitarism]

In 80 patients, 73 cases of pituitary tumours and 7 cases of hypopituitarism, we performed pituitary autoantibodies assays in serum samples because in our previous studies we had found a high prevalence of pituitary autoantibodies in several autoimmune endocrine disorders. To detect the presence of pituitary autoantibodies we applied 2 methods, radioimmunoassay (RIA) and immunoblotting. The RIA was performed by solid phase technique in human pituitary microsome-coated polyethylene tubes. Following incubation with diluted sera of the patients labelled 125I-protein A was added to the tubes to detect the retained antibodies. In the sera of 33 patients we detected the presence of antibodies; in the other 47 patients no antibodies were found. The majority of the patients with positive antibody results were previously treated by pituitary irradiation. To evaluate the molecular weights of pituitary autoantigens the microsomal proteins were separated on SDS PAGE, then electrophoretically transferred to nitrocellulose membranes and reacted with diluted sera of 30 antibody-positive patients. The nitrocellulose strips were incubated with labelled 125I-protein A and autoradiographed. Using immunoblotting, 13 out of these 30 patients we found autoantibodies reacting with pituitary microsomal antigens of different molecular weights, most frequently reacting with a 68 kDa autoantigen.

The prevalence of pituitary autoantibodies in patients with pituitary diseases is 41% lower than in autoimmune endocrine diseases. Pituitary autoantibodies usually appear in patients after pituitary irradiation or after neurosurgery followed by irradiation, but occur rarely in untreated patients with pituitary adenomas.