Hypothalamic-pituitary-adrenal axis function in patients with active rheumatoid arthritis: A controlled study using insulin hypoglycemia stress test and prolactin stimulation

Objective. To study the response of cortisol and of prolactin (PRL) to spec ific stimuli in rheumatoid arthritis (RA). Methods, We measured the response of cortisol to insulin induced hypoglycem ia and of PRL to thyrotropin releasing hormone (TRH) in 10 patients with ac tive RA and in 10 paired control subjects. All were women with regular mens trual cycles. They had never received corticosteroids before the study. The PRL concentration was assessed by chemiluminescence immune assay and the c ortisol concentration by radioimmunoassay. Results. The basal serum levels of cortisol (14.47 +/- 2.5 mu g/dl) and PRL (10.1 +/- 1.3 ng/ml) in the RA group were not significantly different from those of the control group (12.3 +/- 1.1 mu g/dl and 13.7 +/-. 2.4 ng/ml, respectively). The peak value of cortisol after hypoglycemia was comparable in both groups (25.5 +/- 2.4 mu g/dl in RA vs 26.0 +/- 1.5 ng/ml in contro ls). The integrated cortisol response to hypoglycemia expressed as area und er the response curve (AUC) did not differ significantly in either group (1 927 +/- 196 in RA vs 1828 +/- 84 in controls). The interval-specific "delta " cortisol response was significantly higher for the 30 to 45 min interval in controls compared to patients with RA (9.8 +/- 0.9 mu g/dl vs 6.1 +/- 1. 1 mu g/dl; p = 0.02), The peak of PRL after TRH did not differ significantl y in both groups (56.4 +/- 6.4 ng/ml in RA vs 66.3 +/- 7.7 ng/ml in control s) and the AUC of PRL secretion after TRH was comparable in both groups (32 45 +/- 321 vs 4128 +/- 541). Conclusion. Our findings suggest that active RA is associated with subtle d ysfunction of the hypothalamic-pituitary-adrenal glucocorticoid function an d normal PRL secretion.