Macroprolactin is formed by prolactin-immunoglobulin complexes and may cause elevation of prolactin (Prl) concentrations, potentially leading to unnecessary investigations and/or treatment. We have endeavoured to assess the prevalence of macroprolactinaemia in euthyroid women with non-toxic goitre and to assess whether autoimmune thyroid disease may result in an increased prevalence of macroprolactinaemia.
Material & Methods: We measured serum Prl in 182 regularly menstruating women aged 32.7±7.5 years (mean±SD, range 17-46 years) who attended clinic, either for investigation of non-toxic goitre (n=86, age 33.2±7.8 years) or with autoimmune thyroid disease (n=96, age 32.3±7.2 years, Hashimoto thyroiditis, n=91, Graves disease, n=5). All women were clinically and biochemically euthyroid, either without or on treatment with L-thyroxine. In case of raised prolactin (i.e. above 530 mIU/L), macroprolactinaemia was ruled out by a PEG precipitation method.
Results: There was no significant age difference between women with and without thyroid disease (P=0.84). Raised Prl concentrations were found in 10 women with thyroid disease (5.5%), and of those a significant macroprolactinaemia (i.e. reduction of Prl concentrations of more than 60% after PEG precipitation) was found in 9 subjects (4.94%). There were no differences in the prevalence of macroprolactinaemia between women with autoimmune thyroid disease (4 out of 96), and without autoimmune thyroid disease (5 out of 86, P=0.075).
Conclusions: Approximately one out of twenty women with regular menses is likely to have raised serum prolactin that is usually caused by the presence of macroprolactinaemia. Though structure of macroprolactin involves prolactin-immunoglobulin complexes, there is no evidence that autoimmune thyroid disease is associated with raised prevalence of macroprolactinaemia.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.