Gender-related differences in prolactin secretion in pituitary prolactinomas

In pituitary prolactinomas, serum prolactin (PRL) levels usually parallel the tumor size. We conducted a retrospective study to determine differences in PRL production between men and women with prolactinomas. A total of 51 patients, 16 men and 35 women, was studied. We investigated clinical, endocrinological, radiological and histological findings, and estimated the tumor volume (TV) by high-resolution magnetic resonance imaging (MRI). Correlation between PRL level and TV was low in men (R=0.458), in contrast to women (R=0.953), c. Men with prolactinomas showed predominance of large tumors (P=0.0009) with high PRL levels (P=0.0009) and had greater tendencies for cyst formation (P=0.0047). Large prolactinomas tended to be accompanied by cyst(s) (P=0.0051) and hemorrhage ( P=0.0015), both of which were associated with reduced PRL secretion (P=0.0004 and P<0.0001, respectively). When the volume of the cysts and hemorrhage was subtracted from the total TV, correlation between PRL level and TV became greater (R=0.905) with no gender difference. Histological examination demonstrated a sparsely granulated type of lactotroph adenoma with occasional fibrosis, particularly in tumors with hemorrhage and cysts. Although a significant discrepancy between PRL level and TV may exist in prolactinomas when intratumoral hemorrhage and/or cysts are present, there is no essential difference in PRL secretion between the sexes.