This study investigates the pituitary-Leydig cell axis in patients with stage I testicular germ cell cancer (TGCC) followed with surveillance only, in order to evaluate the risk of Leydig cell dysfunction one year after orchiectomy.A retrospective evaluation of reproductive hormones in patients with unilateral stage I TGCC (N=72) without relapse diagnosed between 1990 and 2008. A group of healthy males (N=706) served as controls.Before orchiectomy there were no significant differences in luteinizing hormone (LH) and testosterone (T) levels between human chorionic gonadotropin (hCG)-negative patients and controls, although 33% of the patients were outside the 97.5 percentile when using bivariate LH/T evaluation. At 1-year follow-up there was a significant increase in LH (ΔLH=2.04IU/L, p<0.001), and 57% of the patients had an LH/T relation outside the 97.5 percentile.Patients with stage I TGCC are at increased risk of having an LH/T relation outside the normal range one year after orchiectomy, suggesting insufficient Leydig-cell function. Whether a proportion of these patients will develop manifest hypogonadism and benefit from androgen therapy is yet to be clarified.