| Physiological |
| Infancy |
| Puberty |
| Aging |
| Pathologic |
| Drugs |
| Cirrhosis or malnutrition |
| Male hypogonadism - primary or secondary |
| Tumors |
| Testicular - germ cell, Leydig cell, Sertoli cell, sex cord |
| Adrenal - adenoma or carcinoma |
| Ectopic production of human chorionic gonadotropin |
| Hyperthyroidism |
| Chronic kidney disease and dialysis |
| Rare causes |
| Enzymatic defects of testosterone production* |
| Androgen-insensitivity syndromes* |
| True hermaphroditism* |
| Aromatase excess syndrome |
