Autoantibody to growth hormone in a patient with myasthenia gravis

An autoantibody to GH was detected in the serum from a patient with myasthenia gravis (MG) who had never been prescribed GH. Using an immunoprecipitation technique, this autoantibody was found to belong to the IgG class and had a kappa chain. The dissociation constant of the antibody was 56.8 nmol/l and the binding capacity was 37 nmol/l. Serum samples from another 130 patients, including 37 with MG, were examined, but the GH autoantibody could not be detected. To our knowledge, this is the first report demonstrating the presence of a GH autoantibody.