PRL and Increased circulating prolactin concentration: In patients with hyperprolactinaemia, but not in groups B and C, the effect of metformin on circulating prolactin levels correlated with baseline prolactin levels (r = 0.51, p < 0.001), as well as weakly with the effect of this drug on HOMA-IR (r = 0.34, p < 0.001), 2-h postchallenge plasma glucose (r = 0.25, p < 0.01) and triglycerides (r = 0.29, p < 0.01).