Determination of the frequency of hyperprolactinemia-related etiologies and the etiology-specific mean prolactin levels.

Background: Prolactin (PRL) is a peptide hormone secreted by the anterior pituitary that provides lactation during the postpartum period. The causes of hyperprolactinemia are pituitary tumors, medications, primary hypothyroidism, polycystic ovary syndrome (PCOS), renal failure, idiopathic, and other physiological causes such as pregnancy and lactation. In this study, we aimed to investigate the prevalence of hyperprolactinemia etiologies and the mean/median prolactin levels in different etiologies.

Methods: The patients admitted to our outpatient clinic between January 2009-December 2019 were retrospectively screened from our hospital database with ICD-10 codes. Four hundred patients were included in the study; 69.5% of the patients were women. Their mean age was 43.67±13.42 years, the duration of illness was 7.8±5.6 years. The most frequent causes of hyperprolactinemia were found as follows: 52.5% (N.=210) prolactinoma, 7% (N.=28) gonadotropinoma, 6.5% (N.=26) drug-related, 6.5% (N.=25) PCOS, 5.8% (N.=23) idiopathic, 5% (N.=20) acromegaly, 4.8% (N.=19) nonfunctioning adenoma 2.3% (N.=9) craniopharyngioma. Patients with gonodotropinoma were significantly older, and the patients with PCOS were significantly younger than the patients with hyperprolactinemia due to the other etiologies. Patients with prolactinoma had significantly higher prolactin levels and longer duration of the illness when compared to other etiologies of hyperprolactinemia (168.00* ng/mL [14-23,500] [168]); 8* years (0-39) (5.00) years respectively, *median values, (min-max levels) and (interquartile range), respectively.

Results: There was no significant difference between prolactin levels of other etiologic groups except prolactinoma. Surprisingly, we found PCOS patients with prolactin levels greater than 100 ng/mL and acromegaly or drug-induced hyperprolactinemia with prolactin levels greater than 200 ng/mL. In our study, unlike the literature, macroprolactinemia can be seen alone or together with other pathologies. Except for macroprolactinoma, it is not possible to diagnose according to prolactin level. Similar to the literature, prolactinoma was the most common cause of hyperprolactinemia. The causes of hyperprolactinemia, in order of decreasing frequency, were determined to be gonodotropinoma, drug-related, PCOS, idiopathic, and acromegaly. The range of prolactin detected in PCOS is given as new information. It was found that the pediatric group and the adult group had a similar etiology and PRL level.

Conclusions: A large spectrum of physiologic/pathologic conditions increases the prolactin levels, and prolactin levels may vary from person to person. So, the serum prolactin level alone does not guide a clinical diagnosis or make a differential diagnosis.