The risks associated with a subtotal thyroidectomy are related to damage that my occur to structures in the neck during the inspection and removal of thyroid tissue. Structures that may be vulnerable to damage include the parathyroid glands and the recurrent laryngeal nerves.
The parathyroid glands are four tiny pea-shaped glands that are located in the neck. Two of these glands are located on each side of the neck, lying just beneath each lobe of the thyroid gland. In the normal state, the parathyroid glands produce a hormone called parathyroid hormone, also known as PTH. Parathyroid hormone regulates the level of calcium in the bloodstream through interactions that involve the bones and the kidneys. While performing any type of thyroid surgery, a surgeon must take extreme care to avoid accidentally removing or damaging the parathyroid glands. This may be difficult, as they are very small and may share a common blood supply with areas of the thyroid gland that may need to be explored or removed. If the parathyroid glands are damaged, they may not be able to produce adequate amounts of parathyroid hormone. This may lead to the development of a condition called postsurgical hypoparathyroidism. A patient who develops postsurgical hypoparathyroidism may begin to experience symptoms of numbness around the lips, twitching of the face, or cramping and spasms in the hands and feet as the level of calcium in the bloodstream falls below a normal level. In emergency situations, a patient may need to receive injections of intravenous calcium to reverse these symptoms. In many cases postsurgical hypoparathyroidism proves to be a temporary condition that gradually resolves over time. If postsurgical hypoparathyroidism persists, a patient may have to take supplemental calcium and vitamin D on a regular basis to help maintain an even level of calcium in the bloodstream.
The recurrent laryngeal nerves are long nerve fibers that loop down into the neck, passing beneath the lobes of the thyroid gland to attach to the sides of the larynx. In the normal state, these nerve fibers control the muscles that govern the movement and tension of the vocal cords. While performing any type of thyroid surgery, a surgeon must take extreme care to avoid accidentally cutting or damaging the recurrent laryngeal nerves. If a recurrent laryngeal nerve is damaged, it may impair the movement of the vocal cord. This may lead to the development of a condition called dysphonia. Dysphonia is usually characterized by hoarseness associated with a faint raspy voice. In some cases dysphonia may be a temporary condition that gradually resolves over time. If dysphonia persists, a patient may need to undergo a special operation called a laryngoplasty to reposition and strengthen the impaired vocal cord.