Low prolactin levels as a marker of gestational diabetes in late pregnancy

Aims: Beyond its known role in lactation, prolactin is emerging as a hormone involved in gestational glucose metabolism. This study aimed to assess prolactin trajectories across pregnancy and their association with metabolic outcomes, including gestational diabetes (GDM). Methods: A longitudinal cohort of 120 pregnant women (67 with GDM, 53 non-GDM) was followed throughout gestation. Prolactin, fasting glucose, insulin, and HbA1c were measured each trimester and GDM diagnosed by 75-g oral glucose tolerance test. Postpartum follow-up included breastfeeding and glucose tolerance assessment. Multivariable logistic regression and ROC curve analyses were used to estimate the independent association between third-trimester prolactin and GDM. Results: Prolactin levels were significantly lower in the third trimester in women with GDM (p = 0.027). First-trimester prolactin inversely correlated with fasting glucose (p = 0.02;r = -0.4), while second-trimester values with HbA1c in mid- (p = 0.035;r = -0.5) and late gestation (p < 0.001;r = -0.9). Third-trimester prolactin independently predicted 2-hour glucose post-load (t = -2,5;p = 0.03). A threshold of < 182 μg/L showed 59.5 % sensitivity and 90 % specificity for identifying GDM (AUC = 0.72 ± 0.087,p = 0.009). Logistic regression confirmed this association (p = 0.034). Conclusions: Lower third-trimester prolactin levels are independently associated with GDM and may serve as a hormonal marker of impaired metabolic adaptation. Serial prolactin profiling could aid in endocrine-based risk stratification.