Yes. Your replacement hormones must be high enough to build a uterine lining and then shed it once a month. As we've seen in the research, this hormone action of build and shed extends all the way to the myelin sheath encasing the neurons in your brain. If there is no evidence of this happening in your uterus, then it's not happening in your breasts, brain, or bones, either. The blood levels and a five day bleed with strong bleed on day two or three tell you that you have "virtual fertility". Mother Nature protects the fertile ones.