Macroprolactinaemia: prevalence and aetiologies in a large group of hospital workers

Abstract

Macroprolactinaemia is a common disorder and causes hyperprolactinaemia in a healthy population. The major aetiology of macroprolactin in our subjects was complexes of prolactin-IgG comprising mainly anti-prolactin autoantibodies, and other minor complex prolactin species.

Importance of macroprolactinemia in hyperprolactinemia

“…However, macroprolactinemia may be more common, with a recently reported prevalence of 3.7% and no difference in prevalence between genders [14]. Because the reported proportion of macroprolactinemia in hyperprolactinemic populations is much higher in most studies and varies between 15 and 35% (mean prevalence 25%), macroprolactinemia is therefore considered a common finding in endocrinological practice [3,8,12,13].…”

“…It seems that the hypothalamic negative feedback mechanism by autoantibodybound PRL does not work because the complex cannot access to the hypothalamus due its size and therefore results in mild hyperprolactinemia. However, when serum free PRL concentrations exceed normal PRL concentrations, negative feedback mechanisms begin operating to normalize free PRL levels which are usually in sera from most macroprolactinemic patients within normal range [14,37]. Therefore the biochemical findings of serum estradiol and luteinizing hormone (LH) may be significantly higher in individuals with macroprolactinemia compared with those with true hyperprolactinemia [10,18,37].…”

The natural history of macroprolactinaemia

“…The prevalence of macroprolactinaemia is estimated to be 10-26% in patients with hyperprolactinaemia (4,5,6,7,8,9) and 3.68% in the general population (10). MacroPRL is mainly a complex of PRL with IgG, especially anti-PRL autoantibodies (3,10,11,12,13,14,15). Hyperprolactinaemia is more frequently observed in subjects with macroprolactinaemia probably because there is a delayed clearance of macroPRL due to the large molecular size (10,16).…”

“…Macroprolactinaemia refers to a condition where macroPRL, with a molecular mass O150 kDa, is predominantly present in the sera (3,4,5,6,7,8,9,10). The prevalence of macroprolactinaemia is estimated to be 10-26% in patients with hyperprolactinaemia (4,5,6,7,8,9) and 3.68% in the general population (10). MacroPRL is mainly a complex of PRL with IgG, especially anti-PRL autoantibodies (3,10,11,12,13,14,15).…”

“…The main component is usually little PRL, monomeric PRL with a molecular mass of 23 kDa, but there are other minor forms including big PRL (dimeric PRL) and big-big PRL (macroPRL) (1,2). Macroprolactinaemia refers to a condition where macroPRL, with a molecular mass O150 kDa, is predominantly present in the sera (3,4,5,6,7,8,9,10). The prevalence of macroprolactinaemia is estimated to be 10-26% in patients with hyperprolactinaemia (4,5,6,7,8,9) and 3.68% in the general population (10).…”