Analysis of molecular heterogeneity of PRL is important in patients with hyperprolactinemia

Abstract

Assessment of prolactin level in a medical laboratory is most frequently related to verifying the cause of the problems with fertility. However, hyperprolactinaemia diagnosis by laboratory test often does not reflect the clinical condition of a patient. Patients with hyperprolactinemia, but without characteristic symptoms related to this disorder, undergo further biochemical and/or image diagnosis, which could be harmful to the human organism. In some cases, pharmacological treatment and even surgical intervention are applied, although the cause of elevated prolactin levels has not been identified. Prolactin is present in blood in different forms and/or complexes. Most frequently, three basic isoforms of this hormone are distinguished: monomeric prolactin, big-prolactin, and big-big-prolactin, called a macroprolactin. The listed forms of prolactin have different biological activity, but in laboratory tests, all of them show immunoreactiveness. For that reason, prolactin is a large problem for laboratory diagnosticians and clinicians. The analysis of the presence of macroprolactin in blood samples with elevated prolactin level is not a routine matter, even though it has a key meaning in the further diagnostic process of hyperprolactinemia. A gold standard identifying all forms of prolactin is gel filtration chromatography, which gives qualitative and also quantitative results. Unfortunately, the equipment used for this method is not commonly available in medical laboratory. Results of many studies showed that the precipitation of macroprolactin with polyethylene glycol could be the screening method for evaluating the macroprolactinaemia prevalence. This procedure is simple and relatively low-cost, and though it has some analytical restrictions, its results correlate well with the results of the gel filtration chromatography. Macroprolactinaemia is present in a small percentage of the total population; however, it can occured in 53% patients with hyperprolactinaemia.