Objective:To investigate the clinical characteristics and offer diagnostic and therapeutic approaches for adult-onset idiopathic hypogonadotropic hypogonadism(AIHH).Methods:Clinical, laboratory, and imaging data, as well as follow-up information, of three male patients diagnosed with AIHH at the Department of Endocrinology and Metabolism of Nanfang Hospital, Southern Medical University, were systematically reviewed and analyzed.Results:All three patients were male, with a median age of 39 years(range, 22 to 40). Two patients reported symptoms of enlarged breasts and reduced sexual function, while one case solely reported a decline in sexual function. Physical examination showed that the median length of the penis was 6 cm(range, 5 to 6 cm), and the bilateral testicular volume was 7.96 mL(4.70-8.82 mL). Basal hormone levels at the time of initial visit to our hospital as follows: the median testosterone level was 0.32 ng/mL(0.24-2.96 ng/mL), median follicle stimulating hormone(FSH) level was 0.56 mIU/mL(0.1-0.75 mIU/mL), and the median luteinizing hormone(LH) level was 0.69 mIU/mL(0.1-1.03 mIU/mL). The levels of other hormones secreted by the anterior pituitary gland were normal. Hypothalamic-pituitary magnetic resonance imaging(MRI) showed that 1 patient had a pituitary microadenoma. Three patients were treated with pulsatile GnRH or gonadotropins, one of which had hypothalamic-pituitary-gonadal(HPG) axis function reversal after GnRH pulse pump therapy and lasted for 1 year, but then still had irreversible reduction.Conclusion:AIHH is marked by adult-onset disease and idiopathic hypogonadism. Enhancing fertility remains a critical requirement for these patients. Pulsatile GnRH treatment or gonadotropin therapy, as viable treatments, exhibit therapeutic effects, albeit with occasional fluctuations. Therefore, the emphasis lies in the timely consideration of fertility preservation.