5α-Reductase inhibitors 5α-Reductase inhibitors like finasteride and dutasteride can slightly increase circulating levels of<unk> by inhibiting its metabolism. However, these drugs do this via prevention of the conversion of<unk> into its more potent metabolite dihydrotestosterone (DHT), and this results in dramatically reduced circulating levels of DHT (which circulates at much lower relative concentrations). In addition, local levels of DHT in so-called androgenic (5α-reductase-expressing) tissues are also markedly reduced, and this can have a strong impact on certain effects of<unk>  For instance, growth of body and facial hair and penile growth induced by<unk> may be inhibited by 5α-reductase inhibitors, and this could be considered undesirable in the context of, for instance, puberty induction. On the other hand, 5α-reductase inhibitors may prevent or reduce adverse androgenic side effects of<unk> like scalp hair loss, oily skin, acne, and seborrhea. In addition to the prevention of<unk> conversion into DHT, 5α-reductase inhibitors also prevent the formation of neurosteroids like 3α-androstanediol from<unk>  and this may have neuropsychiatric consequences in some men. Aromatase inhibitors Aromatase inhibitors like anastrozole prevent the conversion of<unk> into estradiol by aromatase. As only a very small fraction of<unk> is converted into estradiol, this does not affect<unk> levels, but it can prevent estrogenic side effects like gynecomastia that can occur when<unk> is administered at relatively high dosages. However, estradiol exerts negative feedback on the hypothalamic–pituitary–gonadal axis and, for this reason, prevention of its formation can reduce this feedback and disinhibit gonadal production of<unk>  which in turn can increase levels of endogenous<unk> <unk> therapy is sometimes combined with an aromatase inhibitor for men with secondary hypogonadism who wish to conceive children with their partners. Cytochrome P450 inhibitors Inhibitors and inducers of cytochrome P450 enzymes like CYP3A4 have been associated with little or no effect on circulating<unk> levels. Antiandrogens and estrogens Antiandrogens like cyproterone acetate, spironolactone, and bicalutamide can block the androgenic and anabolic effects of<unk>  Estrogens can reduce the effects of<unk> by increasing the hepatic production and in turn circulating levels of sex hormone-binding globulin (SHBG), a carrier protein that binds to and occupies androgens like<unk> and DHT, and thereby reducing free concentrations of these androgens.
Testosterone 
Counterregulatory hormone
Menotropin
Luteinizing hormone
Orexin
Adrenocortical hormone
Androgen
Adrenalone