Endocrine Abstracts

Introduction: Macroprolactin (maPRL) is a high molecular weight variant of prolactin (PRL) which has reduced bioactivity. The purpose of the present study was to determine the clinic-analytical repercussion of the presence of maPRL in patients with hyperprolactinaemia.

Patients and methods: A polyethylene glycol (PEG) precipitation test was used to detect the presence of maPRL in all consecutive samples with prolactin levels >50 ng/ml (1060 mUIL). A recovery <75% was taking as indicating of maPRL. Hospital records of subjects with maPRL were review retrospectively.

Results: Over a 24-month period, maPRL was found in 22 (9.6%) of 228 patients with total PRL >50 ng/ml. All patients with maPRL were women; the mean age was 32 years (12–48). Serum PRL levels ranged from 50.5–158 ng/ml. The most frequent reason for the initial PRL request was menstrual disturbance (45% patients). MaPRL was associated with an increase of monomeric PRL level in 36.4% of patients (group A) and in this group hypogonadal symptoms was presented in 87.5%. MaPRL was associated with normal level of monomeric PRL in 63.6% (group B) and in this group only one patient presented amenorrhoea (7.14%), P<0.05. Pituitary adenomas were identified in 2 of 6 who underwent neuroimaging. Dopamine agonist treatment resolved hyperprolactinaemic symptoms.

Conclusions: Our results indicate that patients with maPRL only presented symptomatology suggestive of hyperprolactinaemia when monomeric PRL concentration was elevated. MaPRL has limited clinical repercussions but its determination in routine practice is important in order to avoid inappropriate management.