When people think about estrogen, they usually think about how much of the hormone their body produces. But the other side of this story is how well your body processes and clears estrogen once it's been used. This process, called estrogen metabolism, is just as important as estrogen production itself. One of the body's most important tools for processing estrogen is methylation, a biochemical process supported by the MTHFR gene. MTHFR and hormones are linked.