The thyroid gland is located at the front of neck and controls the body’s metabolism by producing and releasing thyroid hormone. The most common reasons for operating on the thyroid gland are related to symptoms of compression due to enlargement of the gland (goiter), for diagnosis of a thyroid nodule, thyroid cancer, or an overactive thyroid (hyperthyroidism) that cannot be treated with medicine.
Diseases of the thyroid gland
Goiter is an enlarged thyroid gland. Many multinodular goiters do not require surgery unless there are symptoms of difficulty swallowing or breathing due to compression of the esophagus or trachea. The incidence of thyroid cancer in a multinodular goiter is around 10%. If there is a suspicious nodule on ultrasound, a FNA may be recommended for diagnosis.
Thyroid nodules are very common, and fortunately, most (80-90%) of them are not cancer. If a nodule is larger than 1 cm, and/or has suspicious characteristics on ultrasound, a FNA is recommended for diagnosis. A nodule may be observed if the FNA is benign (non-cancerous). If the FNA is suspicious or shows thyroid cancer, then an operation is recommended.
This is a type of thyroid nodule that cannot be classified as benign (non-cancerous) or malignant (cancerous) based upon the FNA. There is a 20% chance that it could be a cancer, therefore an operation to remove the nodule is usually recommended.
The thyroid gland is overactive, producing too much thyroid hormone. Thyroid stimulating hormone (TSH) is suppressed. Excess thyroid hormone causes symptoms of rapid heart rate, sweating, etc.
An autoimmune disorder, is characterized by hyperthyroidism, eye symptoms, and other features. It is usually treated by antithyroid medications and radioactive iodine. Surgery is also an effective treatment that has a quick onset. A toxic nodule or toxic multinodular goiter produces excess thyroid hormone causing hyperthyroidism. Both of these conditions may be treated with thyroidectomy.
The thyroid gland is under-active, producing too little thyroid hormone. TSH is elevated. The symptoms are lack of energy, coarse hair, dry skin, etc. Other than surgical removal of the thyroid gland, the most common cause is Hashimoto’s thyroiditis, an autoimmune disease in which the functioning thyroid cells are slowly destroyed by immune cells. Treatment is thyroid hormone replacement (Synthroid, levothyroxine). Nodules may form and thyroidectomy may sometimes be required for symptoms or diagnosis
The incidence of thyroid cancer is growing in the US and worldwide. Fortunately, it is usually a very treatable cancer with excellent survival rates. The different types of thyroid cancer are papillary, follicular, medullary, and anaplastic. Additional variants are tall-cell, insular, and Hurthle cell carcinoma. The treatment and follow up care of patients with thyroid cancer is multidisciplinary, involving a team of physicians (radiologists, pathologists, endocrinologists, surgeons) and nurses.
Papillary Thyroid Cancer
This is the most common type of thyroid cancer. It occurs more frequently in women. The diagnosis is often made on FNA before surgery. Spread to the lymph nodes is frequent. It usually takes up radioactive iodine, which is used for diagnosis and treatment after thyroidectomy.
Follicular Thyroid Cancer
This is less common. It is typically identified as a follicular neoplasm on FNA, therefore requiring thyroidectomy for diagnostic purposes. Invasion of the capsule or vascular space is its hallmark on pathologic exam. It usually takes up radioactive iodine, which is used for diagnosis and treatment after thyroidectomy.
Medullary Thyroid Cancer
This cancer originates from C-cells, which migrate into the thyroid during embryo development. It produces a tumor marker, calcitonin, which can be detected on FNA with a special stain, or with a blood test. Thirty percent of medullary thyroid cancer is inherited. Medullary thyroid cancer will often spread to the lymph nodes. It does not take up radioactive iodine.
Anaplastic Thyroid Cancer
This is a deadly type of cancer that is most often diagnosed in older individuals. It is fortunately rare. The treatment may involve surgery, chemotherapy, and radiation therapy. The cancer does not take up radioactive iodine as the cells have become dedifferentiated – they no longer act or look like thyroid cells.
Thyroid cancer treatment and follow-up
The mainstay of thyroid cancer treatment is surgery. Removal of all detectable cancer is the goal of surgery. A total thyroidectomy is usually recommended, except in very small papillary thyroid cancers, or in minimally invasive follicular thyroid carcinoma. If there is evidence of lymph node spread, or in some cases of medullary thyroid cancer, removal of lymph nodes in the neck (lymph node dissection) will be recommended. After surgery, the disease stage can then be determined.
In most cases of papillary or follicular thyroid cancer, radioactive iodine ablation will be recommended, followed by a post-therapy radioactive iodine scan which will demonstrate any residual thyroid cells that have taken up the iodine. In cases with a higher chance of recurrence, larger or treatment doses of radioactive iodine will be given. Thyroid hormone will be given to replace the function of the thyroid gland, as well as to suppress any possibly remaining thyroid cancer cells. Thyroglobulin levels will be monitored at regular intervals. To detect recurrences, stimulated thyroglobulin levels and scans may be performed, as well as neck ultrasound scans.
Radioactive Iodine Ablation
The purpose of ablative therapy is to destroy any remaining thyroid cells so that thyroglobulin levels may be optimally used for detection of recurrent disease. The preparation for ablation involves taking the active, shorter acting form of thyroid hormone, T3, or Cytomel until 2 weeks prior to treatment to prevent symptoms of hypothyroidism. A low iodine diet is started 2 weeks prior to treatment. On the day before treatment, blood work is drawn, and a I123 dosing capsule is taken by mouth. On the following day, a whole body scan is done, then the I131 treatment is taken by mouth in liquid form. Thyroxine, the usual thyroid hormone replacement, is started the day after the I131 treatment. A post therapy scan is performed 1 week after ablation to look for evidence of thyroid cancer spread.
Stimulated Thyroglobulin Levels and Scans
Thyroid cells become stimulated by elevated levels of thyroid stimulating hormone (TSH) to increase their production of thyroglobulin and iodine uptake. This feature is used to increase the sensitivity of thyroglobulin testing and RAI scans in the detection of recurrent thyroid cancer. The elevated TSH levels are accomplished by thyroid hormone withdrawal or with the administration of recombinant TSH (rTSH).
This is a surgical procedure to remove the thyroid gland. Part or all of the thyroid gland may be removed (see types of thyroidectomy). An incision (the smallest possible) is made at the front of the neck. Muscles overlying the thyroid gland are moved aside, and the small arteries and veins supplying the thyroid gland are divided and tied off. The superior and recurrent laryngeal nerves controlling the vocal cords (structures responsible for producing the voice) and the parathyroid glands are located next to the thyroid gland and are carefully protected during surgery.
Types of Thyroidectomy
Cervical Lymph Node Dissection
A cervical lymph node dissection if performed if there is papillary or follicular thyroid cancer spread to the lymph nodes of the neck, or in cases of medullary thyroid cancer where there is a high incidence of lymph node spread. The neck is divided into sections (compartments), and only the compartments that are affected are dissected. Every effort is made to preserve the important nerves, blood vessels, and other structures in the neck.
Preoperative Preparation for Thyroid Surgery
Patients with hyperthyroidism will need to have the condition controlled by antithyroid medication and beta blockers (if appropriate) before surgery to avoid the complication of thyroid storm, an uncontrolled release of thyroid hormone. Patients with Graves disease will often be given potassium iodide or Lugol’s solution for 7 to 10 days before the operation to decrease the blood supply to the gland. Other patients undergoing thyroid surgery do not need special preparation.
- Thyroid lobectomy - removing half of the butterfly shaped gland.
- Thyroid lobectomy and isthmusectomy - removing half of the gland and the middle part of the gland.
- Near-total or total thyroidectomy - removing the entire gland.
- Subtotal thyroidectomy - leaves behind a part of the thyroid gland.
- Minimally invasive thyroidectomy – thyroidectomy performed through a very small incision.
- Endoscopic video-assisted thyroidectomy – thyroidectomy performed through several very small incisions, aided by a small camera inserted into the neck.
- Total endoscopic thyroidectomy