Is synthroid/levothyroxine synthetic pig thyroid hormone, as the other brands have typically been real pig

I know that armour brand of thyroid hormone is made from dessicated pig thyroid hormone, but is synthroid n levothyroxine also? I know that synthroid (levo its generic version) is synthetic thyroid hormone. Synthetic hormones are sometimes just a variation of a real hormone. I have never been able to find out much about it. Also, how would a pill properly effect the thyroid hormone from the stomach where it dissolves? How is the correct level expected to travel to the thyroid, what is the rest of the body doing with the unused thyroid hormone that didn't make it to the thyroid. Tweet