Thyroid and Parathyroid Surgery
What and where is the Thyroid Gland?
The thyroid gland is an endocrine organ in the midline of the neck, just below the Adam's apple. It consists of a right and left lobe joined across the front of the windpipe by a strip of thyroid tissue, the isthmus.
The function of the thyroid is to convert iodine taken in the diet, into thyroid hormone (thyroxine). To avoid iodine deficiency in New Zealand soil it is put into table salt. Another major source of dietary iodine is seafood. Diseases of the Thyroid gland are common and can occur when the thyroid produces too much or too little thyroid hormone. In addition, sometimes the thyroid becomes enlarged or develops tumours, which may be benign (non-cancerous) or malignant (cancerous).
Many thyroid p roblems can be treated with medication, but sometimes surgical removal of either part or the entire thyroid is required.
Thyroxine has a major regulatory role for metabolic rate. An overactive thyroid with elevated levels of thyroid hormone in the blood is called Hyperthyroidism. The commonest cause of this condition is an immunological disease call "Graves Disease". The symptoms of hyperthyroidism include tremor, heat intolerance, irritability, increased energy, weight loss and frequently, bulging eyes. The bulging eyes coupled with elevated levels of thyroid hormone are virtually diagnostic of Graves Disease. Treatment of Hyperthyroidism usually involves stabilising the patient with drugs to block the release of thyroid hormone from the thyroid, plus the use of beta-blocking drugs to slow the heart rate. Subsequently definitive management of hyperthyroidism usually involves thyroid ablation with a drink of radio-active iodine (I131) which destroys many of the overactive cells in the gland. However, occasionally thyroidectomy may be a preferred option. Surgery rather than radio-iodine may be indicated to manage hyperthyroidism in children, pregnant or lactating women, as a result of patient preference, or if the hyperthyroidism is due to exposure to the cardiac medication amioderone.
A deficiency of thyroxine from an under-active gland results in a low metabolic rate condition called hypothyroidism. This condition results in tiredness, weight gain, lethargy, and slowness of speech and thinking. The commonest cause of hypothyroidism is an immunological disorder namely Hashimotos Thyroiditis. Hashimoto's Thyroiditis is a type of autoimmune thyroid disease in which the immune system attacks and destroys the thyroid gland resulting in low levels of thyroid hormone in the blood. Treatment is simple with the use of daily thyroxine medication.
Both Hyper- and Hypo-thyroidism are diagnosed by measuring the thyroid hormone levels i n the blood (T4 and TSH, and occasionally T3).
When the thyroid gland grows excessively a swelling called a Goitre forms around the front of the throat. The entire gland may be involved or a single side. Patients with overactive or under-active thyroid glands may also have goiter but most patients with goiters have normal thyroid function. In patients with goiter there is a metabolic defect involving the production of thyroxine and this defect is often familial. Small goiters often do not require treatment but large goiters can cause pressure on the windpipe and gullet. This can result in difficulty swallowing, shortness of breath, chronic dry cough and a sensation of increased pressure in the neck. Surgery to remove the thyroid gland is usually necessary to treat large goiters that are causing symptoms. Surgery is also necessary if there is suspicion of thyroid cancer in one of the enlarged thyroid lumps. (See FNA Below). For large goiters a CT scan is often useful to asses the extent of compression (squashing) of the trachea (windpipe) and also assess the extent of extension of the goiter into the chest. See CT scans in Figs below:
Large Multinodular Goitre Right Lobe is Larger the Left Lobe
Large Goitre causing partial Superior Cava Obstruction
Very Large Goitre with Severely Compressed Trachea
2 Solitary Nodule
A solitary thyroid lump is a common clinical problem. Over 90% of solitary nodules are benign.
The 5-10% of thyroid nodules that are not benign, are usually low-grade cancers which are usually curable. (See FNA & Thyroid cancer below). A solitary thyroid is present in the Fig below.
A cyst is a collection of fluid. Thyroid cysts are common. They can be diagnosed by ultrasound or by needle aspiration. Sometimes draining the cyst makes the cyst disappear. If multiple aspirations are required, resection of the thyroid lobe may be required to exclude a cystic thyroid cancer.
4 Colloid Nodules
These are benign nodules made up of thyroid tissue. They can be single or multiple and can become large. They can generally be diagnosed on fine needle biopsy and surgery is usually not required.
5 Benign Thyroid Tumours (Adenomas)
Although these tumours are benign they often require surgery as differentiating between benign tumours and cancers based on pre-operative fine needle aspiration (FNA) of a thyroid lump and subsequent cytology (looking at the aspirate under the microscope) is not always reliable. As a consequence, surgery is often recommended for diagnosis. This is especially true if the aspirate is reported as: " atypical", or as a "follicular neoplasm". When there is doubt as to the nature of a thyroid lump the patient requires an operation under general anaesthesia. The lobe of the thyroid that has the nodule in it is removed and while the patient is asleep the nodule is frozen and looked at under the microscope (Frozen Section). If the so-called benign lesion is actually a papillary cancer (see below) this can often be diagnosed by frozen section. The other types of thyroid cancer aside from papillary cancer cannot however be reliably diagnosed at frozen section, and if these turn out to be malignant on final pathological assessment (paraffin section pathology), despite the frozen section appearing to be benign (false negative frozen section) a second operation is often required, usually 1-2 weeks after the initial surgery.
The common thyroid cancers are the differentiated cancers:
Papillary cancer: (70% of total)
Follicular cancer: (20% of total)
Hurthle Cell cancer (a sub-group of follicular cancer): (5% of total)
Medullary Cancer (5% of total)
Papillary cancers have a tendency to spread to neck lymph glands while follicular cancers tend to spread by blood to bone and lungs. The prognostic factors for differentiated thyroid cancers are: Age of the patient (young patients do better), the size of the cancer (lumps >4 cm do worse than smaller lumps) and how readily the cancer can be resected with a clear margin of normal tissue. If lymph glands are involved, they are usually removed by performing a neck lymph node dissection (see Neck dissection of website)
In addition, outcomes for thyroid cancer are often improved by employing one or more drinks of adjuvant radio-iodine (I131) to destroy any residual thyroid cancer cells after surgery. This drink has a very few complications.
Medullary cancer is one of the least common types of thyroid cancer. Some types of medullary cancer are familial and as a result may occur in early childhood. Familial medullary thyroid cancers may be associated with the presence of other endocrine tumours involving the adrenal glands, pituitary gland,or other sites. Outcome for medullary cancer depends whether it is the sporadic type or the familial type as well as how early it is detected, how big the primary lesion is, whether lymph nodes are involved, and how high the plasma calcitonin level is. The hallmark of medullary cancer is the production of increased levels of the hormone calcitonin. This hormone is produced by the "C cells or para-follicular cells of the thyroid and is involved in the regulation of calcium metabolism.
Diagnosis of Thyroid CancerPhysical examination
is useful to gauge the size of the thyroid lump and whether it feels benign or malignant, as well as whether there are palpable lymph nodes present.Ultrasound (US)
is useful to assess thyroid nodules and determine whether they are solid or cystic. Ultrasound is also useful to assess whether lymph node involvement is present. In addition US can be useful to guide an FNA biopsy to ensure the right aspect of a lump is the site of the biopsy (US guided FNA biopsy)Fine Needle Aspirate Cytology (FNA).
This is the most important method for evaluating thyroid lumps. A small sample of the thyroid is removed using a small (23 or 25 gauge) needle and this is made into a slide and examined microscopically. The likely readings are:
Surgery is usually performed for options 2 and 3 while a "wait & watch" approach is often used for option 1 whereby sequential ultrasounds are performed over many months looking for interval change in the size of the lump.
Types of Thyroid Surgery (Thyroidectomy)
Surgery of the thyroid may be needed if it is:
Total thyroidectomy (removal of both Right and Left thyroid lobes) is the preferred operation for most thyroid conditions: most thyroid cancers, most goiters, and most over-active thyroids where surgery is considered to be the preferred treatment rather than the more common treatment with radio-iodine.
Following total thyroidectomy, thyroxine tablets must be taken daily for life to replace the thyroid hormone that the thyroid produces. In the short term calcium and/or vitamin D tablets may also be required due to damage to the parathyroid glands which is common during total thyroidectomy but almost always this injury to the parathyroids recovers and long term requirement for calcium replacement is rare.
When a nodule is suspicious for cancer on FNA, but not definitely malignant, removal of half of the gland is often appropriate. In addition a frozen section may be performed while the patient is asleep in order to get a clearer idea whether the suspicious lesion is benign or malignant thereby allowing the opposite side of the thyroid to be removed if need be and preventing the patient having to undergo a second surgery on another day. Frozen Section is a reliable method for diagnosing papillary cancer but is not reliable for diagnosing follicular cancer or follicular variant of papillary cancer (see above under FNA and Frozen section).
Thyroxine is often not requires following removal of only half of the thyroid gland.
Technique of Thyroidectomy
Thyroid surgery is performed under general anaesthesia through an incision in or parallel to a skin crease in the front of the neck. The central neck muscles are exposed and then retracted exposing the Left and Right lobes of the thyroid.
The veins draining blood from the thyroid are tied off as are the arteries supplying blood to the thyroid. The recurrent laryngeal nerves and the superior laryngeal nerves supplying the larynx (voice box) are exposed and avoided. The para-thyroid glands which control blood calcium levels (4 in number: 2 on each side) are preserved on their blood vessel if possible, and if this is not possible, they are transplanted into a nearby muscle where they develop a new blood supply thereby remaining viable. Dissection of the thyroid is performed close to the thyroid capsule specifically avoiding injury to the nerves and parathyroid glands. See Fig below (RLN is recurrent laryngeal nerve):
Once the appropriate extent of surgery has been performed (1 or both sides of the thyroid), with our without frozen section, the wound is closed after placing suction drain(s). These drains are removed usually at 24-48 hours post surgery.
This is when examination of tissue is performed under a microscope while the patient is asleep to determine whether the tissue is malignant or not.
A pathologist comes to the operating suite to perform a frozen section, which usually takes 10-20 minutes. When the tissue examination is complete, the pathologist reports the result directly to the surgeon in the operating room. Depending on the report either the other thyroid lobe is removed or the wound closed. (also see above).Neck Dissection for Thyroid Cancer
Both papillary cancer and Medullary cancer frequently spread to neck lymph glands. The classification of neck nodes is shown in the two figures below. The lateral neck nodes are classified as Levels 1-5, and the central neck nodes levels 6 and 7:
For thyroid cancers with a high risk of recurrence often a central neck dissection is performed at the time of thyroidectomy. For patients who recur in the neck following thyroidectomy the 2 common levels for recurrence to occur are levels 4 and 6. In this latter group of patients lymph glands are usually resected from levels 2 to 6. Level 1 is only rarely involved with thyroid cancer.
A drink of radio-active iodine is often required following surgery for thyroid cancer. This has minimal complications, has been shown to decrease recurrence of thyroid cancer and may be repeated if needed. The main indication for adjuvant radio-iodine treatment is a high likelihood that the thyroid cancer may recur and/or an elevated thyroglobulin level.
Thyroglobulin (Tg) is a protein found in the blood that is only produced by the thyroid. An elevated Tg level following thyroidectomy for thyroid cancer is a very accurate marker of tumour recurrence.
Prior to treatment with radio-iodine a thyroid isotope uptake scan is usually required and during treatment the patient is kept off thyroxine. Being off thyroxine results in an increase in the blood thyroid stimulating hormone (TSH) from the pituitary gland and this elevated TSH blood level promotes the uptake of the radio-active iodine into thyroid cancer cells.
Complications of Thyroid Surgery
All operations involve some risk. Risks specific to thyroid surgery include:
The relevant frequency of conditions requiring thyroidectomy are shown in the Table below which summarizes the Authors experience
Distribution of the Authors Experience of ThyroidectomiesType of Operation & Number Performed
Total Thyroidectomy for Cancer 280
Total Thyroidectomy For Benign Disease 700
Total Thyroidectomy for Toxic Disease 30
Partial Thyroidectomy for Various Reasons 1000
Parathyroid glands are small glands of the endocrine system which are located behind the thyroid and produce parathyroid hormone. Most humans have four Parathyroid glands: two on either side of the thyroid one upper and one lower gland bilaterally. They are small, only a few millimeters in size. Occasionally there may be 5 or more glands, or one may actually be present in the chest, most commonly in the thymus gland behind the breast bone.
Note the superior parathyroid glands are close to the back of the superior part of the thyroid, while the inferior parathyroid glands are close to the inferior aspect of the thyroid gland occasionally arising in the thymus (see b above).
The purpose of the parathyroid glands is to regulate the blood calcium level within a very narrow range so that nerves, muscles, and brain can function properly. Any decrease in the blood calciumlevels stimulates the parathyroid glands to release parathyroid hormone into the blood. This in turn results in an increase in the blood calcium level with the level returning into the normal range.
The major disease of parathyroid glands is over-activity of one or more of the parathyroids which results in the over-production of parathyroid hormone or "hyper-parathyroidism". This abnormality results in an elevation of the blood calcium level called hypercalcaemia.
By far the most common (90% of cases) cause of hyper-parathyroidism is a benign tumour in one parathyroid gland: a Parathyroid Adenoma.
The next most common situation (9%) is a condition whereby all 4 parathyroid glands are abnormal. This is called Parathyroid Hyperplasia.
Only rarely is the condition caused by a Parathyroid cancer (<1%).
Primary hyperparathyroidism is quite common: The condition affects women three times more often than men and becomes progressively more common with age. Approximately 1 woman in every 200 over the age of 40 yrs has hyper-parathyroidism.
Most patients do not have any symptoms and the condition is diagnosed when the patient has a blood test that shows a high blood calcium level. Some people do, however, have symptoms and these may include: aching in the arms and legs, osteoporosis and bone fractures; kidney stones; stomach ulcers and abdominal pain. In older patients with severe disease mental confusion may occur.
Once a diagnosis of hypercalcaemia is made, other tests are usually required to diagnose hyperparathyroidism. Most important is the determination of the blood parathyroid hormone level. In some patients it is also important to check the urine calcium level. Other tests that may be required include measurement of kidney function and the bone enzyme alkaline phosphatase
Surgery for Hyperparathyroidism
Occasionally drugs are used to temporarily bring down the level of calcium if the level is very high. The only definitive treatment, however, is surgical removal of the overactive parathyroid gland or glands. Usually this is a highly successful procedure with a low complication rate.
The object of the operation is to locate and remove the overactive parathyroid tissue (most commonly one gland as in Fig below).
Minimally Invasive Parathyroidectomy
Pre-operative localization of the overactive gland may be possible by performing an ultrasound scan and or an isotope scan using the tracer Sestamibi which is taken up by the parathyroid tissue. If one gland can be identified pre-operatively to be overactive on both the ultrasound and the sestamibi scans, then a smaller incision can often be possible to the side of the midline of the neck and a simpler and quicker operation performed. However, if the overactive gland(s) cannot be identified, the standard operative procedure is to use an incision in the midline of the neck similar to that used for thyroid surgery and examine all 4 parathyroid glands and remove the abnormal one(s). Again this is a very successful operation with a low complication rate.
The operative technique involves a low curved neck incision. The thyroid is partially mobilised to explore one or more parathyroid glands. The enlarged gland(s) is/are removed. Sometimes a frozen section is performed to confirm the presence of parathyroid tissue. Hospital stay is usually 1-2 days and recovery 1-2 weeks.
Complications of Surgery for Hyperparathyroidism
As with thyroid surgery, the potential complications of surgery for parathyroid disease include:
Patients with chronic renal (kidney) failure who are on dialysis often develop hyperparathyroidism. This involves all four parathyroid glands and results in calcium being mobilized out of bones with resultant bone pain. Parathyroid surgery may be required often depending on the degree of PTH elevation. This type of parathyroidectomy cannot be performed using minimally invasive surgery and the goal is to remove at least three and a half parathyroid glands.