GNRH1 and breast cancer: Several previous studies have elucidated the effects of GnRH agonists plus endocrine therapy on gonadotropins and sex hormones in premenopausal women with HR+ breast cancer (Kurebayashi et al., 2017; Lee et al., 2020; Masuda et al., 2011; Noguchi et al., 2016; Wu et al., 2021).