Prolactin deficiency in rheumatoid arthritis.

Prolactin and growth hormone were determined from the sera of 48 patients with rheumatoid arthritis (RA) and 23 controls by radioimmunoassay and by the Nb2 lymphoma proliferation bioassay. A highly significant deficiency was found in the bioactivity of circulating prolactin (PRL) in patients with RA, whereas immunoactive PRL was near normal. Only age matched male patients showed significantly lower serum PRL levels by radioimmunoassay. Patients with RA with anemia and high reticulocyte counts had bioactivity of PRL elevated and those with anemia and low reticulocyte counts had a decreased bioactivity of PRL when compared to patients without anemia. Prolactin isolated from the sera of 5 patients with RA showed decreased bioactivity in comparison with PRL separated from 5 sex matched controls. Serum factors capable of enhancing or inhibiting the response of Nb2 cells to ovine PRL were also discovered. Our results indicate that RA is associated with PRL deficiency.