Prolactin (PRL) is a polypeptide hormone with a molecular weight of 32 kDa formed by 199 amino acids. It is produced by lactotropes, acidophil cells of the anterior lobe of the pituitary. PRL synthesis occurs also in other parts of the brain and in some peripheral blood elements. This explains partly the controversial and divergent conclusions of hitherto published work. PRL was included also among immunomodulating factors and the hypothesis of its possible participation in the pathogenesis of autoimmune diseases was assumed. Different functions of PRL are known but little is known about the mechanism of action of this hormone, induction and action in target cells. There are many reports on the more frequent occurrence of higher PRL levels e.g. in patients with systemic lupus erythematosus (SLE) but little is known on possible associations of hyper-PRL and the activity of the disease, type of treatment of SLE, duration of the disease and in particular specific organ affections. Another equally important issue is the lack of uniformity as regards sampling of PRL and assessment of its level. Very frequently the influence of external factors which may considerably modify the PRL levels is neglected. Standardization of conditions for PRL assessment and attention paid to external factors during sampling could hasten research of this problem and partly unify some hitherto published studies.

        Key words: hyperprolactinaemia, methods of saturation analysis, radioimmunoanalysis, systemic lupus erythematosus