The relationship between low prolactin and type 2 diabetes

Area of Science:

• Endocrinology
• Metabolic Diseases
• Epidemiology

Background:

• Prolactin (PRL) is a hormone with established roles in reproduction and known pathological effects at elevated levels.
• The clinical significance of low circulating PRL levels remains less understood.
• Type 2 diabetes is a major global health concern with complex contributing factors.

Purpose of the Study:

• To conduct a meta-analysis investigating the association between low prolactin levels and the risk of type 2 diabetes.
• To synthesize evidence from both cross-sectional and cohort studies to evaluate this relationship.

Main Methods:

• Meta-analysis of five cross-sectional studies (8,720 men, 3,429 women) and four cohort studies (2,948 men, 3,203 women).
• Exclusion of participants with conditions affecting PRL levels (pregnancy, lactation, hyperprolactinemia, pituitary disease) or on relevant medications.
• PRL levels categorized by quartiles, with varying cut-off values across studies.
• Type 2 diabetes diagnosis based on physician diagnosis, fasting glucose, OGTT, or HbA1c.

Main Results:

• Cross-sectional studies showed significantly higher odds of type 2 diabetes in individuals with the lowest PRL levels compared to the highest (Men: OR 1.86, Women: OR 2.15).
• Cohort studies revealed a significant association between low PRL and type 2 diabetes in women (OR 1.52) but not in men (OR 1.44).
• Heterogeneity was low in cross-sectional studies (I² 25-38.4%) but higher in cohort studies (I² 52.8-79.7%).

Conclusions:

• Low circulating prolactin levels are associated with an increased risk of type 2 diabetes.
• The observed discrepancy in the association between low PRL and type 2 diabetes in men versus women within cohort studies warrants further investigation.
• Additional research is needed to clarify the role of prolactin in type 2 diabetes pathogenesis and its differential impact across sexes.