Clinical and laboratory features greatly overlap in patients with macroprolactinemia or monomeric hyperprolactinemia

The aim of this study was to evaluate the clinical and laboratory features of 64 patients with macroprolactinemia and to compare them to those of individuals with monomeric hyperprolactinemia.

The study included 64 patients (54 women and 10 men) with macroprolactinemia and 96 patients (70 women and 26 men) with monomeric hyperprolactinemia (32 with prolactinomas).

Symptoms related to prolactin (PRL) excess were found in about 44% of individuals from the macroprolactinemia group and in 88.5% of patients with monomeric hyperprolactinemia (P<0.0001). However, the frequency of menstrual disturbances (oligomenorrhea or amenorrhea), galactorrhea and erectile dysfunction did not differ in both groups. In contrast, the association of galactorrhea and menstrual disturbances was significantly more prevalent in women with monomeric hyperprolactinemia. Although mean PRL levels were higher in patients with monomeric hyperprolactinemia (565.9+/-2726.4 vs 113.3+/-94.5 ng/mL, P<0.001), there was a great overlap between both groups. Among macroprolactinemic patients, pituitary magnetic resonance imaging revealed an image suggestive of a microadenoma in 7 (10.9%) and a macroadenoma in 1 (1.6%). Normalization of PRL levels during therapy with dopamine agonists was significantly more frequent in patients with monomeric hyperprolactinemia than in subjects with macroprolactinemia (78.6% vs 32%, P=0.0006).

Our data show that symptoms related to PRL excess are frequently found in subjects with macroprolactinemia. Moreover, no clinical or laboratory features could reliably differentiate macroprolactinemic patients from those with monomeric hyperprolactinemia. Therefore, the screening for macroprolactin should not be restricted to asymptomatic patients.