Endocrine Abstracts

Objective: Hyperprolactinemia is the most common abnormality of the hypothalamic–pituitary axis. In the majority of patients with hyperprolactinemia monomeric prolactin (monoPRL) namely PRL with a molecular weight of 23 kDa predominates. But, in some patients with hyperprolactinemia high molecular weight forms of PRL namely macroprolactin (macroPRL) is detected. We aimed to investigate the clinic and radiologic features associated with the macroPRL.

Methods: We evaluated 337 patients with elevated serum PRL concentrations who applied to our Endocrinology outpatient clinics. Patients with hypothyroidism and renal failure were excluded. The diagnosis of macroPRL is made if PRL value in the supernatant is <40% of total PRL after precipitation with polyethylene glycol.

Results: Mean age was 33.8±10.8 (16–66) years and male/female was 29/308. Eighty-eight of the patients (26.1%) had an elevated macroPRL level (Group 1) and 249 of the patients (73.9%) had an elevated monoPRL level (Group 2). Two groups were sex-matched (P=0.091); however, mean age of Group 2 was higher than Group 1 (35.0±10.1 vs 30.7±9.8, P=0.016). Mean PRL levels (ng/ml) of the Group 1 and Group 2 were similar (168.0±347.0 vs 238.8±584.9, P=0.239). Frequency of amenorrhea, infertility, irregular menses, gynecomastia and erectile dysfunction were similar in both groups (23.6 vs 11.9%; 7.1 vs 4.7%; 44.6 vs 34.5%, 12.0 vs 25.0; 72.0 vs 50.0, respectively, P>0.05). Rate of asymptomatic patients was higher in Group 1 (30.2 vs 12.0%, P=0.006). Patients with galactorrhea (57.1 vs 39.2%, P=0.04) and abnormal magnetic resonance imaging (MRI) findings (81.1 vs 65.3%) (P=0.02) were more prevalent in Group 2 (57.1 vs 39.2%, P=0.04). In MRI, 54.5% of Group 1 had microadenoma, 6.8% had macroadenoma and 4.5% had empty sella; 64.7% of Group 2 had microadenoma, 14.0% had macroadenoma, 1.2% had empty sella and 1.2% had hypophysitis. MacroPRL levels were not significantly different between idiopathic hyperPRL (34.2±18.5), drug-induced hyperPRL (18.9±21.0), and prolactinomas (24.2±20.5) (P=0.136). MacroPRL percentages of patients with normal MRI findings were higher than patients with microadenoma and macroadenoma (50.2±28.7 vs 35.7±28.1 and 31.8±31.7, respectively, P=0.021).

Conclusion: Existence of high macroPRL level should be considered as a biochemical variation of hyperprolactinemia that may lead to any symptom and that may be accompanied by any radiological findings.