Thyroid Anatomy and Function
The thyroid is a butterfly-shaped gland in the neck that consists of two lobes with a narrow isthmus between them. It lays over the trachea, or windpipe. The gland makes thyroid hormone, an important regulator of metabolism. Overproduction of thyroid hormone is called hyperthyroidism. Symptoms of hyperthyroidism include nervousness, irritability, heat intolerance, rapid heartbeat, muscle weakness, fatigue, frequent bowel movements, light menstrual periods, weight loss, and hair loss. Under production is called hypothyroidism. Symptoms of hypothyroidism include decreased energy level, feeling cold, muscle pain, slowed thinking, constipation, long menstrual periods, weight gain, brittle nails and hair, and depression.
A nodule is a lump of tissue in the thyroid gland and commonly occur. The gland may develop one or many nodules and most of the time do not affect the production of thyroid hormone or cause symptoms. It may or may not be possible to feel thyroid nodules. Most are benign, but on occasion they may be malignant. A goiter is enlargement of the thyroid gland which may or may not be due to nodularity. Patients may be able to see or feel a swelling in the neck and experience local compressive symptoms such as pain, lump in the throat sensation, difficulty swallowing or breathing, or hoarseness/change in voice.
Thyroid Function Tests are blood tests that can help diagnose hyperthyroidism (excessive thyroid hormone production) or hypothyroidism (underproduction). The thyroid is also examined by physical exam. Ultrasound is a routine imaging study that can be performed in the office, but very commonly patients are referred to a surgeon after having one. The ultrasound can identify nodules and cysts, provide precise measurements of these lesions, and identify other features that may be suspicious for cancer. A thyroid scan is a nuclear medicine test that can identify whether nodules are “hot” (excessive thyroid production) or “cold” (not producing any hormone). Hot nodules can be associated with hyperthyroidism and are typically benign. Cold nodules are more likely to harbor malignancy in about 10- 20% of cases. Fine Needle Aspiration (FNA) biopsy can help determine if a thyroid nodule is malignant. The FNA may be performed in the office by the surgeon, or by an endocrinologist, primary care physician, or interventional radiologist. Any nodule over 10 mm meets size criteria for FNA. Austin Surgeons utilize the Afirma gene expression classifier system (AFIRMA). This FNA is performed with the patient comfortably reclined with their head tilted slightly back. Only a minimal amount of local anesthesia is required. The test requires 4 passes of a skinny needle into each nodule that needs biopsy. Ultrasound is used to guide and confirm precise placement of the needle within the nodule. The cells that are in the needle aspirate and are then prepared and sent to a group of physicians trained to evaluate thyroid cells (cytopathologists).
There are two phases of evaluation by the cytopathologist. First, they evaluate stained cells under the microscope. If findings are clearly benign, no further testing is necessary. Some patients may still require surgery due to nodule size, symptoms, or other circumstances. If the Afirma FNA findings are malignant, no further testing is necessary and surgery will be scheduled. In these clear benign or malignant scenarios, FNA results are sent to the surgeon in several days. If FNA results are indeterminate on the initial stained cell evaluation, the cells are evaluated genetically, which may take up to 2 weeks.
Prior to this testing, most of those nodules required surgery. The genetic testing provides better information on whether thyroid surgery is necessary and reduced the numbers of unneeded operations.
Small, stable, and asymptomatic nodules may not require specific treatment other than periodic follow-up with the surgeon, endocrinologist or primary care physician.
Surgical removal of part or the entire thyroid is necessary if an enlarged gland is symptomatic, for significantly enlarging nodules, and if cancer is suspected or confirmed. If a cancer has been diagnosed, treatment after surgery with radioactive iodine, administered by an endocrinologist, may also be necessary.
Treatment for an overactive thyroid can include medications, radioactive iodine treatment, or surgery (total thyroidectomy).
Thyroid surgery requires general anesthesia. The incision is approximately two inches long and is placed at the base of the front of the neck in a natural skin line or crease. The incision is closed with dissolvable sutures below the skin and overlying Steri-Strip or skin glue dressings. Surgery usually involves removing either the entire thyroid gland (total thyroidectomy) or just one lobe (lobectomy).
Total thyroidectomy is generally recommended if the entire gland is abnormally enlarged or multinodular and symptomatic, for hyperthyroidism, or after a cancer diagnosis.
A lobectomy is recommended if there is a concerning nodule in only one lobe. This nodule may be large and symptomatic, overactive, or suspicious for being a cancer.
Often it is not possible to know with certainty if a nodule is cancerous prior to surgery, so the suspicious nodule via a lobectomy is removed to determine this. If the nodule is malignant, it may be necessary to remove the other lobe as well (completion thyroidectomy) on another day to allow the pathologist evaluating the specimen to render their final report Occasionally, but not routinely, removal of lymph nodes may be necessary if cancer is present.
After the operation, the patient is carefully observed in the recovery room until the anesthetic effects wear off. After a lobectomy, the patient can often can go home the same day, while after a total thyroidectomy, a patient typically spends at least one night in the hospital. After a total thyroidectomy, it is necessary to monitor calcium levels. The parathyroid glands are four tiny glands found near the thyroid gland which regulate calcium metabolism. They are often closely adhered to the thyroid, and require separation from it during surgery. This can affect their function for a short time, especially following total thyroidectomies. Patients are placed on calcium supplements after surgery until the parathyroid glands have resumed normal function.
Patients may eat and drink after surgery as tolerated. We encourage patients get up and walk. A sore throat and mild hoarseness are common. Cool fluids, throat lozenges and voice rest may help. Patients may shower the day after surgery and should follow-up in the office about one week after surgery.
Although complications are rare, there are risks associated with thyroid surgery. They include:
- Bleeding (commonly referred to as hematoma) in the neck operative field. This requires immediate attention. Risk of occurrence is less than 1%.
- Infection risk is less than 1%.
- Injury of nerves going to the vocal cords. This can lead to temporary or permanent hoarseness. Risk is less than or equal to 1%.
- Injury of the parathyroid glands with resulting permanent low blood calcium level. Risk is less than 1%. Temporary low calcium levels are not uncommon especially following total thyroidectomies, typically not severe and are managed with calcium supplements as noted above.
Complications from anesthesia
Patients should call the office if they experience increasing swelling at the incision site (some swelling is expected), severe pain, bleeding, signs of infection, a temperature over 100.4 F degrees, persistent numbness or tingling around the lips or extremities, or muscle cramping (signs of low calcium).
Parathyroid Anatomy and Function
Typically, there are four parathyroid glands located in the neck, in proximity to the thyroid gland. Normal parathyroid glands are soft, flat, and approximately the size of a grain of rice. Their function is to control calcium homeostasis, essentially the body’s calcium thermostat. When calcium levels fall and demand increases, within minutes the extremely sensitive parathyroid cells will produce and release parathyroid hormone (PTH) which, in turn, increases the reabsorption of calcium from the bones and kidneys, raising the calcium to normal levels. Conversely, when the calcium levels are normalized or elevated, PTH production and release is reduced and calcium can deposit back in bone and be excreted in the urine. Under normal circumstances, when calcium levels are high, PTH levels should go down and when calcium levels are low, PTH should go up. These actions help maintain calcium levels in a range vital to a body’s normal function.
Primary hyperparathyroidism occurs when there is excessive or inappropriate secretion of PTH by one or more of the parathyroid glands leading to higher than normal calcium levels (both PTH and calcium levels high). This is the most common reason patients are referred to our practice. In approximately 85% of patients, one of the four parathyroid glands is overactive, due to benign enlargement of a single gland called an adenoma. Some patients have more than one abnormal gland, termed hyperplasia. The elevated PTH in hyperparathyroidism causes resorption of calcium from bone thereby weakening the bones, a condition known as osteoporosis or osteopenia. Additionally, elevated levels of calcium in the urine and can result in kidney stones and, over time, permanent kidney damage. Patients with elevated blood calcium levels also often suffer from fatigue/lack of energy, muscle weakness, memory or concentration lapses, irritability, insomnia, depression, excessive thirst and urination, reflux/indigestion, and risk of cardiac and pancreatic problems. About a third of patients with this condition are minimally or non-symptomatic.
An elevated blood calcium coupled with an elevated PTH level establishes the diagnosis. Occasionally, a physician may request a 24-hour urine collection for calcium. Patients then typically undergo a radiologic study known as a parathyroid scan using a Sestamibi radioactive marker in conjunction with a special CT and/or ultrasound to locate the abnormal parathyroid gland.
Surgery is the only curative treatment and we use state of the art, minimally invasive techniques. The operation is usually simple, safe, quick, and done on an outpatient basis. In approximately 80% of patients with hyperparathyroidism, the offending gland can be seen and localized on preoperative sestamibi imaging. Those patients with positive sestamibi scans are candidates for Minimally Invasive Radioguided Parathyroidectomy (MIRP). Austin Surgeons was the first group in Austin and Central Texas to perform the MIRP procedure and has the most parathyroidectomy experience in the area. During the MIRP procedure, the patient receives a preoperative dose of the same sestamibi radioactive marker used for their prior scan study. No further images are required. The sestamibi concentrates in the abnormal parathyroid and can be found more easily with the aid of a sensitive hand held radioactivity detecting probe. This allows the surgeon to remove the offending gland using a rapid, directed approach, minimizing dissection and operative time. Additionally, in most cases we employ intraoperative PTH (IOPTH) monitoring. A blood PTH level is drawn preoperatively, then intraoperatively we recheck the PTH using a rapid assay following removal of the bad gland to confirm success and herald the operations end. The operation is usually performed under general and local anesthesia, through a very small incision at the neck base in a natural skin line or crease, and takes thirty minutes to an hour to complete. Following the operation most patients are discharged within a few hours.
The approximately 20% of patients with a negative sestamibi scan have the same disease, hyperparathyroidism, but their offending glands do not take up the marker and are not visible. These patients undergo the time honored and highly successful “parathyroid exploration” in which all 4 glands are identified and appropriately managed.
Our surgeons routinely utilize IOPTH blood test monitoring to check levels of the parathyroid hormone before and after removing the abnormal glands and employ radioguided and ultrasound techniques as noted above.
Nearly all patients go home within a few hours of the procedure. Depending on job requirements, patients often return to work as early as the next day and are seen in the office for follow up in one week. We typically advise a calcium supplement like TUMS or Citrucel once or twice a day for 1 week because of “hungry bones.” More may be needed if the patient develops symptoms of low calcium including numbness or tingling of the lips or extremities or cramping. To reduce pain and swelling, an ice pack for 15-20 minutes often helps. If there is no contraindication, we advise using over-the-counter pain meds such as Ibuprofen, Aleve, or Tylenol, as needed. A prescription for a narcotic pill may be prescribed, but is usually not necessary.
Although complications are rare, there are risks inherent in all parathyroid surgery. They include:
- Hoarseness related to the proximity of voice box nerves to the parathyroid tissue.
- Low calcium levels may occur for a few days and are treated with oral calcium supplements for the first week. Long term persistent low calcium that requires treatment is rare (1%).
- Complications common to all surgeries such as infection or postoperative bleeding are rare (1%).
- Despite our best efforts, in approximately 1% of patients we are unable to locate the diseased gland resulting in persistent hyperparathyroidism (usually due to an ectopic (abnormal) location of the gland, sometimes in the chest.