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Parathyroidectomy
Removal of the parathyroid gland

The parathyroids are endocrine glands intimately involved with calcium balance. They secrete parathormone (PTH) in response to low serum calcium and secrete less PTH when the calcium is normal or high. The incidence of hyperparathyroidism in the general population is 25/100,000 people. It is most common in women after menopause and in women greater than 65 years of age the incidence rises to 2.5/1000.

Anatomy and Physiology

  • The parathyroid glands are typically four in number. (Figure1) The glands may be found anywhere from the mandible to the pericardium (sac that covers the heart) but are mostly behind the middle or upper third of the thyroid gland. The parathyroid glands are not found behind the thyroid gland in about 10% of cases. They are yellow-brown to red-brown in color, 5-6 x 3 x 1-2 millimeters in size and 35 - 40 grams in weight
    1. The glands may be in the capsule of the thyroid, beneath it or within the thyroid
    2. The blood supply to the parathyroid glands is from the superior and inferior thyroid arteries
    3. The glands have an intimate relationship with the recurrent laryngeal nerves that control the vocal cords
  • Under the microscope, parathyroid tissue in adults shows three kinds of cells:
    1. Chief cells that secrete Parathormone (PTH). The usual adenoma (tumor) is of chief cell origin
    2. Oxyphil cells, appear at puberty, and can cause hypercalcemia (increased blood calcium)
    3. Fat cells are few in number but increase at puberty
  • Serum calcium is regulated as follows:
    1. A decrease in serum calcium causes a rise in PTH which in turn causes a rise in 1,25-(OH)2D3 (metabolite of the natural form of vitamin D3)
    2. PTH and 1,25-(OH)2D3 then cause calcium and phosphorus to come out of bone and enhance intestinal absorption of calcium and phosphorous. For vitamin D3 to be active it is converted in the liver to 25-hydroxyvitamin D3 (25-OH D3). The 250OH D3 is further converted in the kidney to 1,25-dihydroxy-vitamin D 3 (1,25-(OH)2D3). People who have had their kidneys removed cannot convert vitamin D3 to its active form and consequently cannot raise their serum calcium
    3. High serum calcium results in lower levels of PTH and 1,25-(OH)2D3.
    4. The usual dietary intake of calcium is between 500 milligrams to 1000 milligrams per day. Calcium is excreted in the urine normally 100 - 200 milligrams per day, sweat up to 100 milligrams per day, and the remainder in the stool. Calcium absorption is mainly in the duodenum and jejunum
    5. Calcium is frequently tied to bone density alone but it has many other functions. Calcium has major roles in nerve function, muscle contraction, cardiac muscle contraction, hormone release and function of body cells

Pathology

Hyperparathyroidism (increased PTH with elevated calcium) is the most common reason for parathyroid surgery and comes in several forms:

  • Parathyroid adenoma - a benign (noncancerous) tumor with unregulated release of PTH. A single adenoma is found in 70-80% of cases and double adenoma in 4-5%
  • Parathyroid hyperplasia - a diffuse enlargement of all the parathyroid glands with unregulated release of PTH. It is found in10-15% of cases and is a difficult operative diagnosis
  • Multiple Endocrine Neoplasia Type - familial syndrome with abnormalities of thyroid, adrenal, and parathyroid glands usually producing hyperplasia of the parathyroid glands
  • Parathyroid carcinoma (cancer) - a rare cause and less than 1%
  • Familial Hyperparathyroidism - genetic in nature, inherited and rare
Figure 1 - Side view of the parathyroid glands on the back side of the thyroid gland. Note the relationship of the recurrent laryngeal nerve.© C. Scalici

History and Physical

  • Symptoms that may occur are muscle weakness, fatigue, depression or bone pain
  • On examination there may be a mass in the neck. This is rare and is suspicious for a cancer
  • Kidney stones and bone disease are commonly associated with hyperparathyroidism
  • Hypertension may occur and be related to kidney damage associated with kidney stones that form with hyperparathyroidism
  • Frequently, there may be an increase in blood calcium found on screening blood studies

Tests

  • Hypercalcemia due to hyperparathyroidism can be accurately diagnosed with two laboratory tests carried out on blood serum:
    1. Serum calcium concentration - a persistent increase in serum calcium on repeat samples (upper limit of normal is 10-10.2 milligrams per deciliter)
    2. PTH radioimmunoassay - a measure of PTH in the serum through the use of a radioisotope
  • Additional laboratory tests that may be used are:
    1. Ionized serum calcium - a measure of salt form of calcium in the blood
    2. Urinary calcium - the amount of calcium in the urine
    3. Serum and urinary phosphate
  • Imaging studies may be helpful in the diagnosis of a parathyroid adenoma or in determining where the adenoma is located
    1. Ultrasound - can be used to determine the position of a parathyroid adenoma. (Figure 2) Ultrasound probes can be used in the operating room to identify the parathyroid glands
    2. Computer axial tomography - a CAT scan is helpful in finding adenomas in the mediastinum (space between the lungs) and in telling parathyroid glands from lymph nodes
    3. Magnetic Resonance Imaging - similar information to CAT scans
    4. Technetium Sestamibi scan - a radioactive isotope is injected that is taken up by the parathyroid adenoma. (Figure 3) This helps in deep neck and mediastinal areas. The isotope may be injected preoperatively and probes used in the operating room to identify the glands
    5. Angiography - a dye that shows up on X-ray is injected through a catheter into the arteries feeding the parathyroid glands. This can identify areas of increased vessels that may represent increased functioning tissue of the adenoma
    6. Venography - following arteriography the veins in the region of the parathyroid glands are sampled for PTH levels, high levels point to the area where the parathyroid gland may be found

     

Figure 2 - Ultrasound of a parathyroid tumor. The arrow heads outline the thyroid gland. Courtesy J. Bender, MDFigure 3 - Sestamibi scan of a parathyroid tumor seen on ultrasound in figure 2. Courtesy J. Bender, MD

Indications and Contraindications

  • Severe forms of hyperthyroidism are an indication for surgery. The mild and moderate forms may not all require surgery. A Consensus Development Conference of the National Institute of Health in 1990 gave the following indications for surgery with minimal hyperparathyroidism (no symptoms):
  • Serum calcium greater than 11.5 to 12 mg/dL
  • Creatinine clearance (kidney function study) reduced more than 30% for age in the absence of another cause
  • 24-hour urinary calcium greater than 400 mg/dL
  • Bone mass reduced more than 2 standard deviations compared with age, gender and race-matched controls
  • Patients who request surgery or in whom long-term surveillance is unsuitable
  • Young patients (< 50 years of age) Contra indications are poor general health or limited life expectancy

Surgical procedure

  • Single adenomas are the most common cause of hyperparathyroidism and because of better imaging identification of these adenomas preoperatively is better and allows a smaller, more directed operation. All the parathyroid glands no longer are necessarily investigated as in the more typical operation
  • The recurrence rate for hyperparathyroidism following parathyroidectomy is around 10%
  • The procedure is as follows:
    1. The patient is placed under anesthesia with a tube in the trachea (windpipe) to keep the airway open during the procedure
    2. The patient lies on his back with the neck tipped back as far as possible by placing a roll under the shoulders
    3. A curved incision is made just above the base of the neck (Figure 4). The incision is carried towards the thyroid gland. The small neck muscles (strap muscles) lying in front of the thyroid gland are dissected off the thyroid gland and retracted to the side
    4. The lateral lobes of the thyroid gland (See Thyroidectomy) are dissected free and rolled to the midline to expose the back of the thyroid. The dissection is carried out in the tissue immediately behind and slightly below the thyroid lobes to identify the usual four parathyroid glands. This search may extend posteriorly (behind) to the grove between the trachea and esophagus, superiorly (above) it may extend well above the thyroid following the vessels and esophagus, inferiorly (below) it may go behind the sternum (breastbone)
    5. Care is taken to Identify and preserve the recurrent laryngeal nerves that control the vocal cords (See Laryngectomy...coming soon)
    6. All of the glands are inspected and the degree of parathyroid operation is determined by the cause of the hyperparathyroidism
    • Single adenoma with the other three glands being normal - biopsy at least two of the gland and possibly three for microscopic study to determine that the biopsied structures are parathyroid glands and appear normal. The normal glands are biopsied before removing the larger gland with the adenoma. The adenoma is removed (Figures 5,6,7) and followed by microscopic examination. This is the operation in 70-80% of cases i. If more than one adenoma is found then both are removed ii. Interest is growing in doing a urinary cyclic AMP determination while the patient is on the operating table. This is an indicator of active PTH that lasts only a few minutes. A prompt fall of the chemical in the urine may provide evidence that the hyperparathyroidism has been corrected
    • Diffuse hyperplasia - careful inspection of all the parathyroid glands is carried out. Each gland is biopsied and if everything indicates diffuse hyperplasia then 3 1/2 parathyroid glands are removed
    • Parathyroid carcinoma - the involved parathyroid gland, adjacent tissues, the thyroid lobe on side of tumor and any identified lymph nodes are removed
    • Occasionally the involved parathyroid gland may be within the thyroid or thought to be in the thyroid gland. A thyroid lobectomy is indicated

     

Figure 4 - Incision for removal of parathyroid tumor. © C. ScaliciFigure 5 - Parathyroid adenoma as seen from the side. © C. Scalici
Figure 6 - Parathyroid adenoma being excised. © C. ScaliciFigure 7 - Adenoma removed. © C. Scalici

Complications

  • Bleeding
  • Infection
  • Airway obstruction
  • Vocal cord paralysis due to recurrent laryngeal nerve injury (1% of cases)
  • Hypocalcemia (low blood calcium) is frequent in the early period after surgery and is rarely permanent (3%). This may require treatment with vitamin D3 and calcium for a short period
  • Hypoparathyroidism (low parathyroid hormone) - is usually permanent and due to insufficient functioning parathyroid tissue. This requires life long calcium and vitamin D3 replacement
  • Recurrent hyperparathyroidism - occurs in about 5% of patients
  • Lung problems such as atelectasis (insufficient expansion of the lung) and pneumonia

Postoperative care

  • Routine vital signs are taken including blood pressure, heart rate, respiration, and temperature
  • The neck is observed for swelling and difficulty with the airway
  • Urine is measured
  • The patient is walked as soon as possible and encouraged to take deep breathes and cough
  • Serum calcium studies are taken - the surgeon likes to see a significant early drop in calcium
  • Tetany (forced contraction of muscles) can be caused by low calcium and exhibit tingling of fingers, twitching of facial muscles and a postive Chvostek test (tap on facial nerve in front of ear to see if corner of mouth moves)
  • Intravenous fluids are given for at least 24 hrs. Eating and drinking are encourages early
  • Pain medication is given as necessary
  • Supplemental calcium and vitamin D3 is given as needed
  • The patient is usually discharged in 1-2 days after surgery

Care After Discharge

  • Follow in the surgeon's office is usually in 5-10 days
  • Serum calcium is followed at regular intervals
  • The patient can usually drive a car in 2-3 days and return to work in 2-4 weeks