BACKGROUND Inhibin B and antimüllerian hormone (AMH) are secreted by the Sertoli cells, stimulated by gonadotropins. We evaluated their use for discriminating between congenital hypogonadotropic hypogonadism (HH) and constitutional pubertal delay. MATERIAL/METHODS Group 1 (n=39) was diagnosed with constitutional pubertal delay; group 2 (n=15), isolated HH; and group 3, pituitary stalk interruption syndrome (3a with [n=5] and 3b [n=8] without HH). RESULTS At pubertal age, mean plasma inhibin B concentrations were similar in the groups having the same gonadotropin status. Individual concentrations were normal in groups 1 and 3b, but low in 6 group 2, and 3 group 3a patients. Four group 2, and 1 group 3a, also had low AMH. Among these 9 with low inhibin B, 1 in each group evaluated before puberty had had normal inhibin B and AMH. In contrast, inhibin B increased (P<.03) and AMH decreased (P<.02) in 7 group 3b patients from before to after puberty. There were 20 patients with inhibin B below 100 pg/mL including 4 group 1, 13 group 2, and 3 group 3a. The basal plasma follicle stimulating (FSH) and luteinizing (LH) hormone concentrations were < 1 IU/L in 18%, 36% in group 1, and in 56% and 100% in group 2. CONCLUSIONS Before puberty, plasma inhibin B and AMH concentrations may be normal despite HH. At pubertal age, both are low in some patients with HH. These hormone values may help discriminate between HH and constitutional pubertal delay together with plasma FSH and LH.