If the billiary tree of the liver is plugged significantly, over time, it will no longer perform some of it's functions well. More specifically, the liver is important in converting the T-4 Thyroid hormone into T-3, which is the physiologically active hormone needed for regulation of metabolism and other functions. Conversion of 4 to 3 does not just take place in the liver, but a lot of it does. I have read reports that as much as 80% occurs in the liver.
After numerous flushes, I found I no longer needed the Thyroid med's I had been taking for 15 years. It happened rather quickly. Over about a one month period, in which I had completed 3 flushes, I went from my normal Thyroid dose to none. I reduced the dose because of the typical reaction one has to excessive Thyroid hormone supplementation (rapid heart beat, flushing, anxiety feelings, etc.). When I reduced the Thyroid, the symptoms went away. The next flush brought some on again, and I reduced the supplementation again and got relief. So, within a month, no more supplements and no negative symptoms. All is completely normal.