Mildly elevated serum prolactin level may be a protective factor for preventing thickening of the carotid intima-media in patients with type 2 diabetes mellitus

Objective: To evaluate the correlation between the serum prolactin (PRL) level and carotid intima-media thickness (CIMT) in patients with type 2 diabetes mellitus (T2DM). Methods: In this study, 1,500 participants were divided into three groups based on the serum PRL level: hypoprolactinemia group (PRL ≤ 7 μg/L), normal PRL level group (7 μg/L < PRL ≤ 25 μg/L), and homeostatic functionally increased transient PRL (Ho-PRL) group (25 μg/L < PRL ≤ 100 μg/L). The independent-sample Kruskal-Wallis test was used to compare the CIMT among the three groups. The Spearman correlation test was used to examine the relationship between the CIMT, serum PRL level, and clinical data. Multivariate linear regression analysis was used to determine the independent factors that influence the CIMT. Result: Individuals in the Ho-PRL group had a significantly lower CIMT compared to the hypoprolactinemia and normal PRL level groups (P < 0.001). The CIMT was positively correlated with age, systolic blood pressure (SBP), body mass index, duration of T2DM, and luteinizing hormone and follicle-stimulating hormone levels and negatively correlated with alanine transaminase and aspartate transaminase activities, estimated glomerular filtration rate, and PRL. Multivariate linear regression analysis revealed that only PRL was negatively associated with the CIMT, while age and SBP were positively associated with the CIMT. Conclusion: In patients with T2DM, a PRL level within the mildly elevated range is negatively correlated with the CIMT. A mildly elevated serum PRL level may be a protective factor for preventing thickening of the carotid intima-media.