ABSTRACT. We tested the hypothesis that mutations in NR5A1 and PIN1 cause disorders in gonadotropin-gonadal system development and function, throught direct DNA sequencing of the coding sequence and splice-sites of NR5A1 and PIN1 in 50 subjects with sporadic idiopathic hypogonadotropic hypogonadism. These patients were recruited from the Pediatrics section of Tongji Hospital, Tongji Medical College, in Wuhan, China. None of the affected subjects had clinical signs of adrenal insufficiency. The NR5A1 and PIN1 mutations were found in 7 of the 50 cases. These 7 individuals presented severely low serum concentrations of testosterone or of estradiol and gonadotropin. Adrenal insufficiency was not diagnosed in any of these patients. Consequently, NR5A1 and PIN1 mutations should be considered in idiopathic hypogonadotropic hypogonadism patients with normal karyotypes and without adrenal insufficiency.