PGR and uterine corpus leiomyoma: The reason that SPRMs may provide a solution for treating HMB comes from the mounting evidence that progesterone, and the progesterone receptor (PR), play a pivotal role in both menstruation and in the growth and development of uterine fibroids (Bulun, 2013; Maybin and Critchley, 2016; Wagenfeld et al., 2016).