Dihydrotestosterone is synthesized from testosterone in the prostate gland, testes, hair follicles and adrenal glands by 5-alpha reductase. Dihydrotestosterone exerts its action similar to testosterone, which binds to and activates androgen receptors. Dihydrotestosterone is responsible for the formation of male primary sex characteristics and most male secondary sex characteristics during puberty, such as muscular growth, facial and body hair growth, and deepening of the voice. Excess DHT can cause hair loss, prostate volume increase, and acne. Blocking or decreasing DHT to low levels may cause sexual dysfunction. It is important to test DHT in addition to Testosterone Free & Total, which must be ordered separately. ~CPT code change effective 01/2019 from 80327 to 82642 for reimbursement purposes only.