Final answer:
Estrogens are used to treat prostate cancer by inhibiting testosterone activity, and synthetic derivatives in oral contraceptives prevent ovulation through a negative feedback mechanism.
Step-by-step explanation:
Two therapeutic agents that work by altering hormone control mechanisms include estrogens used in prostate cancer treatment and oral contraceptives. Estrogens can be used to block the release and activity of testosterone, thereby inhibiting prostate cancer growth which is testosterone-enhanced. On the other hand, oral contraceptives usually contain synthetic derivatives of female sex hormones, which prevent ovulation by providing continuous low levels of estrogen and/or progesterone, thereby triggering a negative feedback mechanism that stops the release of hormones that stimulate ovulation.