Serum prolactin levels and mortality in adults without prolactinoma: A meta-analysis

Purpose: Prolactin is a highly versatile, multifunctional hormone synthesized and secreted by lactotroph cells of the anterior pituitary. Its metabolic role has been extensively studied even in normoprolactinemic populations. Recently, a wealth of observational data outlines the potential prognostic value of prolactin in various clinical settings. This systematic review aims to systematically evaluate and quantitatively synthesize the association between serum prolactin levels and risk of mortality in adults without prolactinoma.

Methods: A systematic literature search was conducted up to June 10, 2023 to identify studies reporting the association of serum prolactin levels with clinical outcomes of adults without prolactinoma. A random-effects meta-analysis was conducted to quantify the adjusted hazard ratios [(a)HRs] for all-cause and cardiovascular death during follow-up.

Results: Twenty-eight studies were deemed eligible reporting the outcomes of adults without prolactinoma, in whom serum prolactin levels were measured for risk-stratification. Fourteen studies reported appropriate data for meta-analysis encompassing a total of 23,596 individuals. Each unit of prolactin increase was independently associated with increased risk of all-cause (pooled aHR=1.17 [1.08-1.27]; I2=48%) and cardiovascular mortality (pooled aHR=1.54 [1.14-2.09]; I2=89%). Individuals belonging to the highest prolactin category had significantly higher risk for all-cause (pooled aHR=1.81 [1.43-2.30]; I2=65%) and cardiovascular (pooled aHR=1.59 [1.04-2.42]; I2=82%) mortality compared to their lowest prolactin category counterparts. The association between prolactin levels and in-hospital death did not reach statistical significance.

Conclusions: Prolactin levels seem to be an independent predictor for mortality. Further validation is warranted before its role as a risk stratification tool can be delineated in clinical practice.