ESR1 and adenomyosis: Both LNG-IUD and ENG-SCI release progestin, but differently, the former was attributed to its direct action on down-regulation of estrogen receptor of uterine endometrial and its decidualization to reduce menstrual flow [27], and its pain-relieving ability was obtained by reducing prostaglandin production in the endometrium and inducing atrophy of adenomyosis foci [19], while the latter was based on ovulation inhibition to eliminate the estrogen-ovulation peak, decreasing the average level of estrogen in the menstrual cycle, thus thinning the endometrium.