Association between systemic lupus erythematosus, rheumatoid arthritis, hyperprolactinemia and thyroid autoantibodies

Hyperprolactinemia (hyperPRL) has been associated with autoimmune rheumatic disorders and the presence of thyroid autoantibodies (tAb). The interrelation between these variables was the focus of this prospective study.

The study assessed six groups of individuals: 26 with systemic lupus erythematosus (SLE), 20 with rheumatoid arthritis (RA), 28 with tAb (tAb+), 14 with untreated hyperprolactinemia (hyperPRL), 10 with treated hyperPRL, and a control group (n = 28). Prolactin (PRL), free thyroxin, TSH, antibodies against thyroglobulin (TgAb), thyroid microsomal antigen (MsAb) and/or thyroid peroxidase (TPOAb) were determined in all patients. Those with hyperPRL had macroprolactin investigated by the polyethylene glycol (PEG) precipitation method.

PRL (ng/mL) levels in the SLE, RA, and tAb+ groups were, respectively, 21.3 +/- 12.6, 11.5 +/- 7.4, and 12.5 +/- 8.6, and were significantly greater in the SLE group (p = 0.006) than in the controls (12.5 +/- 6.5) and in the other groups. Five patients had hyperPRL: three with SLE, one with RA, and one with tAb+. Macroprolactinemia was detected in three of the untreated hyperprolactinemic patients and in the hyperprolactinemic patient of the tAb+ group. Positivity for any of the tAb was 15% in the SLE, 15% in the RA, 57.1% in the untreated hyperPRL, 10% in the hyperPRL on treatment, and 3.6% in the control group. The presence of antibodies was significantly more frequent in the untreated hyperPRL group than in the control group (p = 0.001).

The results indicate that the PRL level is higher in SLE patients and that in the presence of hyperPRL there is increased prevalence of antithyroid antibodies, evidencing the association of PRL and autoimmunity and pointing to the appropriateness of assessing and monitoring the progress of these markers in patients affected by these disorders.