Menopause stops the secretion of sex hormones and periods. As the growth of fibroids is dependent on these hormones, they tend to involute and calcify at the time of menopause and they do not cause problems any more.
The hormone replacement therapy for menopause (HRT) can have different roles depending on the types of drugs, it appears that some of them have no effect on the growth of fibroids, others increase their growth but without modify the symptoms.