Relevance and therapeutic implication of macroprolactinemia detection using PEG 6000 in women of childbearing age with hyperprolactinemia: experience at a tertiary hospital

Introduction: Macroprolactin may interfere with hormonal assay and falsely increase serum prolactin levels. Therefore, failure to identify macroprolactinemia can lead to inappropriate investigations and treatment in women already susceptible to anxiety and stress. The aim of this study was to identify macroprolactinemia among women of childbearing age with hyperprolactinemia. Materials and methods: A cross-sectional study was conducted in a tertiary care setting at the endocrine unit. Study participants were recruited from both endocrine and gynaecological outpatient consultation services. They were women of childbearing age (18 to 49 years) consulting for signs and symptoms of gonadal dysfunction or hyperprolactinemia (PRL > 25 ng/ml). Total prolactin was measured using a Human direct ELISA method. Polyethylene glycol 6000 (PEG 6000) precipitation was used to detect macroprolactin. Results: A total of 33 women with a mean age of 31 ± 7 years (range 21–48) were enrolled. Twenty-seven (81.8%) participants were symptomatic, the majority (23/27) (69.7%) reported having galactorrhoea, and 21 (63.4%) women reported having an irregular menstrual cycle. The median pre-precipitation prolactinemia reduced significantly after PEG precipitation from 61.2 (IQR 33.2–115.9) ng/ml to 33.8 (IQR 17.9–70.5) ng/ml, p < 0.001. After PEG precipitation, five participants had a serum prolactin recovery rate below 60% and, therefore, a prevalence of macroprolactinemia at 15.2%. Four out of five (80%) women with macroprolactinemia presented with the symptoms amenorrhea, oligomenorrhea, and galactorrhoea. Conclusion: PEG 6000 permitted the detection of macroprolactinemia in women of childbearing age with hyperprolactinemia who otherwise would have been subjected to unnecessary medical investigations and treatment.