Particularly, men with PRL levels < 5.0 ng/ml or ranging 5.1–7 ng/ml showed a higher prevalence of diabetes mellitus, dyslipidaemia, severe erectile dysfunction and partial erection at the International Index of Erectile Function as compared to those with higher PRL levels [47, 72], together with a higher prevalence of mild depression in men with PRL levels below 3 ng/ml under chronic dopamine agonists treatment [72]. The gene discussed is PRL; the disease is major depressive disorder.