Hyperprolactinaemia has been associated with the active phase of human systemic lupus erythematosus and rheumatoid arthritis. In the present study, we investigated the role of prolactin (PRL) in relation to the number of typical symptoms and serum markers of systemic inflammation in patients with polymyalgia rheumatica (PMR).
One hundred and two PMR patients presented with typical symptoms such as adynamia, bilateral muscular pain in shoulders, upper arms or neck, bilateral muscular pain in the pelvic girdle, headache, morning stiffness, arthralgia, symptoms of depression, fever, initial weight loss (>4 kg/month), and transient visual symptoms. If one of the mentioned symptoms was present, the corresponding item was scored with one point (maximum unweighted item points=10). PRL, interleukin-2 (IL-2), IL-6, IL-1 receptor antagonist (IL-1ra), tumour necrosis factor (TNF), soluble IL-2 receptor (sIL-2R), and soluble vascular cell adhesion molecule (sVCAM) were measured by enzyme-linked immunosorbent assay in patients and 31 age-matched healthy controls.
Fifteen PMR patients with elevated PRL had a higher number of symptoms as compared with patients with normal levels (P=0.003). PRL was correlated with the number of symptoms (all PMR patients: r(rank)=+0.380, P<0.001) and duration of morning stiffness (all PMR patients: r(rank)=+0.335, P=0.002) irrespective of prior corticosteroid treatment. However, PRL did not correlate with markers of systemic inflammation such as erythrocyte sedimentation rate, C-reactive protein, serum IL-1ra, IL-2, sIL-2R, IL-6, TNF, and sVCAM.
The number of symptoms in PMR patients was positively correlated with PRL, but PRL was not correlated with serum markers of inflammation. This indicates that PRL is not a pro-inflammatory stimulus in patients with PMR. The inter-relationship between PRL and symptoms or duration of morning stiffness may be more a sign of central nervous system involvement, as it can be observed in people with depressed mood or under psychological stress.