Bioactivity of prolactin in systemic sclerosis

OBJECTIVES: To evaluate basal serum prolactin (PRL) levels in systemic sclerosis (SSc) patients with different degrees of skin involvement, and investigate its relationship with some of the clinical and serological parameters of the disease. METHODS: Basal serum PRL was measured in 44 SSc patients (38 F, 6 M) using a rat NB2 lymphoma line cell proliferation assay. Other parameters measured were: serum aminoterminal propeptide of type III procollagen (PIIINP) by RIA; soluble alpha interleukin-2 receptor (IL-2 sRalpha), serum intercellular adhesion molecule-1 (ICAM-1), von Willebrand factor (vWF) by ELISA; the erythrocyte sedimentation rate (ESR); and C-reactive protein (CRP). Skin and organ/system involvement were assessed according to Medsger et al.'s organ/system severity scale, and global disease activity index according to Valentini et al. RESULTS: The serum PRL concentration in the SSc patients was 13.8 ng/ml (95%CI from 3.2 to 49.1 ng/ml), similar than that in control subjects (12.8 ng/nl: 95%CI 3.0 to 18.4 ng/ml). Hyperprolactinemia, defined as a level > 20 ng/ml (mean 30.9 ng/ml, median 29.3) was found in a total of 6 cases (13.6%; 95%CI 5.8 to 28%) cases: in 1 out of 6 men (16.7%; 95%CI -26% to 59%) and similarly in 5/38 women (13.2%; 95%CI 1.9% to 24.4%). No correlation was found between PRL levels and SSc subgroup (lcSSc, icSSc, dcSSc), serologial parameters, or the level of disease activity. Finally, no significant correlations were found with clinical or serological variables. CONCLUSIONS: The findings confirm that mild hyperprolactinemia occurs in at subgroup of SSc patients. However, prospective studies are needed to better define the relationship between PRL and disease activity in scleroderma.