Endocrinological and symptomatic characteristics of patients with late-onset hypogonadism classified by functional categories based on testosterone and luteinizing hormone levels

Objectives To define the characteristics of patients with late-onset hypogonadism based on endocrinological findings. Methods We assessed age, body mass index, laboratory/endocrinological profiles and symptom-specific questionnaire scores of 967 men with late-onset hypogonadism symptoms. The patients comprised four groups by testosterone and luteinizing hormone concentrations: normal group, compensated hypogonadism group, primary hypogonadism group and secondary hypogonadism group. We compared characteristics between the normal group and compensated hypogonadism group in men with normal testosterone concentration, and the primary hypogonadism group and secondary hypogonadism group in hypogonadal men after age adjustment. Results The normal group, compensated hypogonadism group, primary hypogonadism group and secondary hypogonadism group accounted for 83.6%, 3.4%, 0.8% and 12.2% of patients, respectively. Despite age adjustment, serum dehydroepiandrosterone sulfate and insulin-like growth factor 1 concentrations were significantly lower in the compensated hypogonadism group than the normal group. Only the Aging Males' Symptoms scale mental subscore was significantly different. Serum testosterone and dehydroepiandrosterone sulfate concentrations were significantly lower in the primary hypogonadism group than the secondary hypogonadism group. Only the Aging Males' Symptoms scale sexual subscore was significantly different. Conclusions Most patients with late-onset hypogonadism symptoms are in the normal group, with secondary hypogonadism being much more frequent than primary hypogonadism. Current symptomatic differences among these groups are minor. Classifying patients by testosterone and luteinizing hormone levels might provide useful information for follow up.