Generally, if you have normal levels, it's not going to help you, except that you would not have to worry about PCT - post cycle therapy - - but HRT for that reason alone seems a little foolish.
Some basic stuff From
http://www.andrologyaustralia.org/pageContent.asp?pageCode=LOWTESTREPLACE
What are the side-effects of testosterone therapy?
Testosterone therapy can increase prostate growth, possibly making any prostate cancer, if present, worse. Testosterone should not be prescribed for men with prostate cancer. It may also make symptoms of benign enlargement of the prostate (or benign prostatic hyperplasia, BPH) worse (for example, obstruction of urine flow or a need for urination more often).
Other side-effects are uncommon. Mild acne, weight gain, breast development (gynaecomastia), male-pattern hair loss and changes in mood (including increased aggression) can happen and should be managed by a doctor.
Sometimes testosterone therapy can increase red blood cells (polycythaemia) leading to problems with blood circulation. This is more likely to be a problem for older men, particularly if they have sleep apnoea (short periods where breathing stops during sleep, often in men with heavy snoring).
Existing tendencies towards migraines, sleep apnoea or androgen-sensitive epilepsy can also worsen with testosterone treatments.
Does testosterone therapy affect fertility?
Testosterone treatment generally stops the production of pituitary hormones FSH and LH which normally stimulate the testes. This reduces the size of the testes and can lower or stop sperm production. If sperm production was previously normal, it usually recovers several months after stopping treatment. Androgen deficient men often don’t make sperm and are already infertile before treatment starts.
Testosterone treatment does NOT boost sperm counts and any man with fertility issues must discuss these with his doctor before starting treatment. Men with low sperm counts wishing to have children may benefit from other hormonal treatments that turn sperm production back on.