- Known serum testosterone ≤ 150 ng/dl or symptoms of hypogonadism (fatigue, hot flashes, hair loss, loss of muscle mass, osteoporosis, low libido, depression) prior to ADT initiation not explained by other medical co-morbidity OR history of testosterone supplement. If questionable, serum testosterone level greater than 150 ng/dl can be used to exclude hypogonadism.