A 44-year old women visited her gynecologist complaining of abdominal pain and abnormally heavy bleeding during menstruation. The doctor discovered that she had fibroids, which are non-cancerous tumors of the muscular layer (myometrium) of the uterus. They discussed various treatment options and attendant risks, including the option of doing nothing. Fearing the risks, the woman decided to do nothing and live with the discomfort. What convinced her was her doctor saying that in a few years, the tumors would shrink by themselves and the problem would go away. Which one of the following provides the best explanation for why the problem would go away in a few years?