The core problem of total thyroidectomy is that it involves a close neighbor of the thyroid gland, the parathyroid gland. It is not an exaggeration to say that the thyroid gland and the parathyroid gland are really within the same layer of the peritoneum, although they are very close, they are not of the same magnitude. One is a big giant and the other is a small dwarf. The parathyroid glands also have the ability to be “chameleons”, as they are mixed in with the fat around the thyroid gland and are almost identical in color, with minimal differences in color. It is this intimacy and the camouflaged color of the parathyroid glands that makes total thyroidectomy so difficult, because the essence of total thyroidectomy is to take away the “huge” thyroid gland without affecting in any way the “small” parathyroid glands that are working at full power. If the patient has permanent hypoparathyroidism, the patient’s quality of life is very low. In addition to the symptoms mentioned above, the muscles all over the body are stiff and need to be relieved by medication or fluids several times a day. Since there are so many difficulties in removing the thyroid gland without affecting the parathyroid glands and the blood supply to the parathyroid glands, there is another way to remove the thyroid gland, and that is to “cut” it from the middle, leaving the “half-pulled thyroid gland” that is intimately connected to the parathyroid glands. This is known as a sub-total thyroid cut; and then there is a diagonal shoulder shovel back cut, leaving 1/4 to 1/3 of the gland in the parathyroid gland, which is known as a sub-total cut. So what is the “second” thing about subtotal thyroidectomy? First, it is difficult to guarantee the completeness of the surgery. It is important to understand that the reason for preserving some of the glands is to preserve the parathyroid glands rather than to meet the needs of the disease. Second, the difficulty of secondary surgery increases. If there is a recurrence of the residual gland after several years, surgery is very difficult because it is very difficult to find the laryngeal recurrent nerve in the original area where the scar has been formed, and even more difficult to find the parathyroid glands, which is almost impossible. Third, it is difficult to ensure follow-up treatment. If follow-up treatment is needed, such as iodine 131, a large amount of iodine 131 is absorbed by the residual thyroid gland and does not reach the tumor cells. If the residual gland exceeds 1 gram, then it is difficult to guarantee the quality of iodine 131 treatment (American Thyroid Association guidelines), which is the reason why some patients will be asked to operate again by the isotope surgeon first because of the excessive residual gland. The above three reasons are more than enough and will not be repeated. I am often asked why the Creator made four parathyroid glands for the human body, and the heartfelt answer is “only two more, not three more”. This means that there are two chances to make a mistake when separating the parathyroid glands and their hair-thin blood vessels, but never a third or a fourth. In fact, for the thyroid surgeon, this is a great mercy from the God of creation, and one should be grateful for it.