Late puberty. Most cases of delayed puberty are simply variants of normal development and not cause for alarm. Half of all adolescents who experience such delays have a parent or sibling whose growth followed a similar pattern. Depending on the cause, workup will include tests for malnutrition brought on by diseases, medications or eating disorders in addition to growth hormone, testosterone and other hormones.
Late puberty. Overall check of health -- lab tests including blood chemistry, cbc, sed rate, thyroid, celiac screen, urine, growth hormone screen, prolactin level, , pubertal hormones, possibly chromosome study. X-ray of hand called bone age radiograph. The main question is whether the boy. Is just a "late developer" or has a more serious health issue. See a pediatric endocrinologist.