Pituitary-cell autoantibody diversity in sera from patients with untreated Graves' disease

Sera from 22 untreated patients with recently diagnosed Graves' disease (GD) were screened in an immunocytochemical tissue assay for presumptive pituitary IgG autoantibodies, as defined by the presence of immunoreaction with rat and swine pituitary cell types. Forty four patients with Hashimoto's thyroiditis (HT) and 97 healthy subjects were also studied. Anti-pituitary antibodies were found in 14 of the 22 GD sera (64%). Of these, 6 sera reacted with cytoplasmic components of growth hormone (GH) cells, 3 with prolactin (PRL) cells, and 5 with both GH and PRL cells. Yet, none of the immunoreactive sera reacted with human GH, bovine PRL or TSH in dot-blot assays and absorption studies. Anti-pituitary antibodies also occurred in 4 of the 44 HT patients (9.1%) and in 9 of the 97 healthy subjects (9.2%). The frequency of sera revealing anti-pituitary antibodies was significantly higher in patients with GD compared to the groups of HT patients (P less than 0.00005), and healthy subjects (P less than 0.00005). Healthy subjects and patients with HT had a similar frequency of anti-pituitary antibodies (P = 1.0000). These data demonstrate that in thyroid autoimmune conditions antibodies reactive with cytoplasmic components of pituitary GH/PRL cells, may be present in sera from patients with GD. The pathological importance of this observation is at present unknown.