Benign and Malignant Thyroid Conditions

Submitted by Dr. Andreas Lambrianides

The thyroid gland is a bilobed endocrine gland situated on each side of the trachea and oesophagus. Each lobe is about 5cm long, communicating with each other by means of the isthmus. Embryologically the gland develops from a midline ventral diverticulum between the first and second pharyngeal arches, which grows caudally to meet an outgrowth of the fourth pharyngeal pouch. The lower end of the diverticulum gives rise to the glandular tissue, while the rest of the diverticulum atrophies. In simple terms the thyroid gland has a butterfly shape and you can find it at the front of the neck just below the Adam’s Apple. The gland produces thyroid hormone which has a major role in regulating many aspects of health including

The rate of Metabolism, that is, the use of fats, proteins, sugars and starches by the body

Body Weight

Heart Rate

Blood pressure

Mental Alertness

Muscles and Nerves

Growth in children

Iodine, an element found in small quantities in many foods is taken up by the thyroid gland to produce thyroid hormones.

Disorders of the thyroid gland are among the most common medical problems

Overactive thyroid

Underactive thyroid

Goitre

Thyroid cancer

Too much thyroid hormone produced by an overactive gland can cause

Staring eyes which may have a bulging appearances

Restlessness

Increased anxiety

Difficulty in sleeping

Fast heart rate

Increased appetite

Diarrhoea

Dislike of hot weather

Weight Loss

Too little thyroid hormone produced by an underactive gland can cause the following:

Swollen lips and puffy face

Tiredness

Slowed movements, thought and speech

Slow heart rate

Poor appetite

Constipation

Dislike of Cold Weather

Weight Gain

Overactive glands can be treated with radioactive iodine in selected patients. This is taken up destroying many overactive cells. If too much or all of the thyroid gland is destroyed by treatment, the patient has to take thyroid hormone replacement medication. If radioactive iodine is not suitable, other medications can be used to reduce the activity of the thyroid growth to a more normal level. Surgery is recommended if radiotherapy and medication are not effective or suitable. Before surgery you need treatment for your symptoms. To reduce the risk of surgery the symptoms should be brought under control. You may be given medicines to lower the amount of thyroid hormone in the blood. Also iodine may be given to reduce the blood flow, making surgery easier and reducing the risk of heavy bleeding. If you have a fast pulse medication may be given to slow your heart rate.

Treatment of choice for an under active gland is thyroid hormone supplements which can be taken in tablet form. People, who take thyroid hormone supplements, usually need to take them for life and have regular blood tests to monitor the effectiveness of their dose.

When the thyroid gland is larger than normal the swelling produced is called a goitre. A goitre can make breathing or swallowing difficult and may be associated with over or under activity of the thyroid gland. Treatment is necessary if problems are encountered and this can take the form of surgery and or the patient may need treatment for an under or over active goitre.

Thyroid carcinoma accounts for approximately 1.5 % of all malignancy and approximately 0.5% of all deaths from cancer. The mortality rate of 6 persons per million population per year coupled with the low incidence suggest favorable prognosis. Because cancer occurs in approximately 15% of patients with a solitary nodule and clinically silent carcinoma (Under 1 cm) Occur in up to 35% of glands recorded at autopsy or surgery, a selective approach should be used to identify patients when the nodule should be removed. Thyroid carcinoma was documented in 24 cases per million population in 1947, in 39 cases in 1971 and 41 in 1988, the increase from 1947 to 1971 may be secondary to radiation exposure. More than one million people received radiation to the thyroid gland for treatment of benign head and neck diseases such as acne, thymus hyperplasia, keloids and external otitis.

In the USA approximately 12, 000 people are diagnosed with thyroid cancer each year. The major risk factors include radiation exposure and a solitary thyroid nodule. Thyroid nodules are clinically apparent in approximately 15 million people in the United States, yet only 5 % will harbor cancer. Malignancy is more likely to occur in people with a history of thyroid carcinoma. A family history of thyroid cancer, an enlarging nodule on thyroid suppressant therapy, exposure to low doses of radiation to the neck, and development of a nodule in a person of under 14 years of age or over 65 years of age. Patients exposed to low doses of therapeutic radiation have a 1 - 7 % chance of developing thyroid cancer with an increasing risk for at least 3 decades after exposure. The highest risk appears to be in children under the age of 7 years. If a patient has a thyroid nodule and a history of irradiation to the thyroid gland a 40% chance exists of having thyroid cancer.

Classification Of Thyroid Cancers Incidence as %
Papillary 80
Follicular 10
Medullary 5
Hurthle Cell 3
Anaplastic 1
Others.. Lymphoma Teratoma Sarcoma Squamous Cell Metastatic Carcinoma 1

 


Patients with genetic conditions such as Gardener’s syndrome and Cowden’s disease have a higher risk of thyroid malignancy. Gardener’s syndrome is associated with multiple polyps in the gastro intestinal tract and colon cancer and carries an increase risk of developing papillary thyroid carcinoma. Cowden’s disease is an autosomal dominant condition characterized by a mucocutaneous lesions and internal malignancy. Patients with Cowden’s disease are prone to the development of breast cancer, colon cancer and malignant thyroid conditions. Cowden’s disease is associated with goitre in 40% of patients and with thyroid carcinoma in 10% of patients. Medullary Carcinoma is often familial may occur in association with endocrinopathies. Living in iodine deficient area increases the risk of follicular and anaplastic carcinoma. Living in an area of high dietary iodine intake appears to increase the risk of papillary carcinoma. Higher circulating levels of estrogens may minimally increase the risk of thyroid carcinoma. Other factors that appear to increase the frequency of thyroid carcinoma: 

Residences near volcanoes

Possibly alcohol ingestion.

Characteristics of malignant thyroid nodules

History Previous Thyroid Cancer Family history of Carcinoma Cowden’s disease Gardener’s disease Familial Medullary Thyroid Carcinoma Enlarging nodule on thyroid suppressant therapy Exposure to low dose therapeutic radiation Rapidly growing or painful nodule Nodule under 14 years or more than 65 years Hoarseness

Examination and investigations

Hard, fixed nodule Ipsilateral cervical lymphadenopathy Ipsilateral vocal cord paralysis Suspicious or Malignant cytology by FNA (Fine neck aspiration) Hypo functioning "Cold" nodule on radio iodine scan Solid nodule on more than 4 cm in size Complex cyst on ultrasound Increasing serum Thyroglobulin

Papillary carcinoma is the most common type of malignancy involving the thyroid gland. It may be multicentric in up to 80% of cases and it frequently involves both lobes. Histologically they can be pure papillary, mixed papillary-follicular and the follicular variant of papillary carcinoma. Mixed papillary-follicular is most common. Minimal (1 cm in diameter) and occult (less than 1.5cm in diameter) are of interest because their incidence exceeds that of papillary carcinoma greater than 1.5 cm and the prognosis is so good, it mandates a more conservative approach then those greater than 1.5cm. The reported incidence of occult varies from 0.45 % to 13 % of Caucasian individuals in Michigan, 28% of Japanese individuals in Japan and 36% of autopsy specimens in Finland.

Rationale For total Thyroidectomy

Recurrence is lower in patience who have undergone total thyroidectomy

Eliminates the 1% risk of a differentiated thyroid cancer changing to an undifferentiated thyroid cancer.

Recurrent cancer develops in the remaining contralateral lobe in approx 7% of patients and one half of these die of thyroid cancer.

Total thyroidectomy eliminates the microscopic foci of cancer present in up to 85% of patients.

Serum thyroglobulin is a more sensitive marker of recurrence when all normal thyroid tissue is removed

Radio iodine can be used to detect and treat local or distant metastases

The less common type, follicular carcinoma differs from papillary in several ways. Follicular are more often solitary and many follicular carcinomas are discovered in association with areas of iodine deficiency, while papillary tend to occur in high iodine intake. Follicular carcinoma tends to invade blood vessels and metastasizes to distant sites, most commonly blood, lung and brain. Patients with follicular carcinoma may have distant metastases before the primary tumor becomes evident. The incidence of metastases in follicular is as high as 33% . Cervical lymph node involvement occurs in approximately 10% of cases of follicular carcinoma. Follicular carcinoma is less frequently associated with previous radiation exposure. Finally occult follicular carcinoma is rare. The rationale for total thyroidectomy is the same. The main difference is that although follicular is solitary it has a higher incidence of distant and metastases especially lung and bone. Total thyroidectomy facilitates radioiodine ablation of any distant metastases.

After surgery patients are treated with sufficient thyroid hormone to suppress TSH (Thyroid Stimulating Hormone) production and lower the recurrence rates. Monitoring serum thyroglobulin levels is a sensitive and specific method of detecting recurrent disease, Since thyroglobulin is only produced by thyroid tissue it follows that total thyroidectomy should result in undetectable thyroglobulin levels. In extensive studies no metastases were found in patients in whom thyroglobulin levels were undetectable.

Certain factors have a profound influence on prognosis of papillary thyroid carcinoma. Age at the time of diagnosis is perhaps the most important. There is a consistent, direct correlation between age and mortality which increases progressively from children to those over the age of 60. In addition the size of the tumor has an impact on survival. When the tumor is greater than 1.5cm or invades the thyroid capsule, recurrence is more frequent and deaths occur more often. The presence of lymph nodes in patients under the age of 40 has little effect on mortality. In patients over 40 with lymph node metastases the mortality is greater.

Follicular carcinoma that show vascular invasion is the most aggressive carcinoma, a 20 year mortality rate of 84% has been reported compared with 2.8 % in patients with equivocal invasions. Increasing age and the presence with distant metastases is associated with poor prognosis. The size of the tumor and the presence of lymph node metastases do not have important prognostic implications.

Mortality appears to be greater in patients with follicular carcinoma rather than those with papillary carcinoma. Of patients dying of follicular carcinoma approximately 75% succumb to distant metastases and the remainder to locally invasive disease.

Your surgeon needs to know your complete medical history to plan the best possible treatment. Fully disclose all health problems and symptoms you may have had. Some health problems may interfere with surgery, anesthesia, and care after surgery. Give your surgeon a list of all the medicines you are taking or have taken recently. Tell your surgeon if you:

Ever had an allergy to anaesthetic drugs or other medicines

Bleeding heavily after injury or surgery

Have any blood disorders such Hemophilia

Are pregnant, could be pregnant or plan to get pregnant. Some treatments are not suitable during pregnancy because of possible risks to the baby.

A specialist anaesthetist gives the Anaesthetic. Modern anaesthetic drugs are safe with few risks. However, a few people may have serious reactions to them. If you have ever had a reaction to an anaesthetic drug tell your anesthetist or surgeon.

During surgery to the thyroid gland an incision is made in the front of the neck along the collar line, just under the Adam’s apple. The surgeon removes part or the entire thyroid gland taking care to avoid injury to adjacent blood vessels and nerves. Every attempt is made to preserve the parathyroid glands, as they produce PTH (parathyroid hormone) which controls levels of Calcium in the blood). The incision is closed with metal clips or sutures. A drain tube attached to a plastic bottle may be used to prevent fluid accumulation. The drain tube is usually removed one or two days after surgery. The skin closures either dissolve or are removed a few days following surgery.

As you recover from the anaesthetic, you will be sleepy for the first few hours. You will be raised in a sitting position with your neck well supported. This position will help reduce the swelling. Your breathing, pulse, blood pressure, temperature and incision will be monitored regularly. You will also be assessed for signs of low calcium. By the day following surgery, you will be able to sit in a chair and walk short distances. Patients usually stay in hospital for one or two days. Pain relieving medicine will be prescribed. An intravenous line will be providing fluid until you are ready to drink. Swallowing and eating may be difficult for the first day or two. Tell your doctor if you have any of the following:

Breathing difficulty

Muscle spasms

Twitching or tingling in your lips or your finger tips.

Dressing soaked in blood.

Most recover fairly quickly after surgery and you should be able to resume most normal activities after one or two weeks.

Recovery from thyroid surgery is usually uncomplicated, but the following problems may occur:

Difficulty in breathing

Bleeding

Injury to the laryngeal nerve, and this can cause hoarseness. This nerve controls the vocal box. Of every hundred patients one or two will have injury to the laryngeal nerve. Patients with cancer or very large goitre or previous surgery are more at risk of nerve injury.

Damage to the parathyroid glands. Calcium supplements may be needed if calcium levels are low. Of every hundred patients who have total thyroidectomy two will need to take calcium supplements for life due to permanent loss of parathyroid function.

"Thyroid Storm". This is rare, and occurs when too much thyroid hormone is released into the patient’s blood stream during surgery.

If you have had total thyroidectomy you will need to take thyroid hormone replacement medication for the rest of your life.

If all the parathyroid glands have been removed, calcium supplements and other medicines may be needed to maintain calcium levels.

General risks of Surgery:

1. Heart And Circulation Problems, such as heart attacks and clot formation.

2. Wound infections

3. Keloid Scar (overgrowth of scar tissue)

This is intended to provide you with information. It is not a substitute for advice from your surgeon, and does not contain all known facts about the treatment of thyroid gland disorders.

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