Endocrine Abstracts

Prolactin (PRL) exists in different forms in human serum. The predominant form is little PRL (23 kDa) with smaller amounts of big PRL (50–60 kDa), that may be also associated with big big PRL (bbPRL) or macroprolactin (150–170 kDa). A lower biological activity in vivo of bbPRL was reported. Aim of the study was to evaluate the clinical impact of macroprolactin and the association between macroprolactinaemia and polycystic ovary syndrome (PCOS). A group of 115 female patients with diagnosis of hyperprolactinaemia were included in our study. All samples collected from these patients were subjected to a PEG precipitation test to detect the presence of macroprolactin according to Vieira method. Recovery ≤40% was considered indicative of the predominance of macroprolactin form. Forty-four patients presented bbPRL as prevalent form of prolactin, 39 of whom were in reproductive age. By converse, in the remaining 71 patients PEG precipitation test demonstrated a true hyperprolactinaemia. Subsequent MRI studies demonstrated the presence of a pituitary lesion in 58 out of these 71 patients, while the remaining 13 subjects had idiopathic hyperprolactinaemia. As far as the clinical picture was concerned, oligo-amenorrhoea and galactorrhoea were more frequent in macroprolactinaemic in respect to non-macroprolactinaemic patients (46 vs 59%, P<0.019, and 23 vs 39%, P<0.019, respectively). Twenty-five macroprolactinaemic patients were further investigated for the presence of PCOS according to diagnostic criteria of 2003 Rotterdam Consensus Conference. Interestingly, 40% of these patients were found to be affected by PCOS. In conclusion, our data confirm a lower biological activity in vivo of bbPRL as demonstrated by the lower prevalence of oligo-amenorrhoea and galactorrhoea observed in macroprolactinaemic as compared to non-macroprolactinaemic patients. Finally, further studies are needed in order to confirm the possible association between macroprolactinaemia and PCOS.