Complex sentence: High doses of progestogens, via exerting negative feedback on the hypothalamic-pituitary-gonadal axis (HPG axis) through activation of the progesterone receptor, have antigonadotropic properties--that is, they suppress the gonadal production of sex hormones such as androgens.
Split into simpler sentences: High doses of progestogens exert negative feedback on the hypothalamic-pituitary-gonadal axis by activating the progesterone receptor. As a result, they have antigonadotropic properties--that is, they suppress the gonadal production of sex hormones such as androgens.