Thyroid disease: what is it?

Thyroid disease is one of the most common hormonal diseases found in our society today. The most prevalent thyroid gland disorders are hyperthyroidism, hypothyroidism, and thyroid nodules.

Hyperthyroidism means there is too much thyroid hormone, which causes your metabolism to speed up. In many ways it is as if the body is stuck in "overdrive." The heart rate increases, muscles can become weak, and hands can begin to shake with a tremour. Bowel movements can be more frequent, and many people feel a sense of agitation or anxiety.

Hypothyroidism means there is too little thyroid hormone. This lack of thyroid hormone makes most of the body's organs slow down their function. Some people remark that they feel "like an engine that is not running on all cylinders." In many ways the symptoms of an underactive thyroid are opposite to those of an overactive or "hyper" thyroid gland. The heart rate slows, muscles become slow and weak and often ache, bowels become constipated, and people feel less energetic.

A thyroid nodule is an enlarged area or lump of tissue. Thyroid nodules are surprisingly common; how common depends on how hard you look for them. The vast majority of thyroid lumps are benign (not cancerous).

What is the thyroid gland - what does it do?

The thyroid gland is just under the skin in the front of your neck, just below your Adam's apple, and can be felt with your fingers (Figure 1). The thyroid gland is important because it produces thyroid hormones, which are necessary for the normal function of virtually all organs in the body. The 2 most important thyroid hormones are thyroxine (T4) and triiodothyronine (T3). These hormones, along with thyroid stimulating hormone (TSH) can be easily measured by taking a blood sample.

The thyroid gland

The role of the pituitary gland

The pituitary gland makes TSH and releases it into the bloodstream (Figure 2). TSH travels to the thyroid and causes the thyroid to release the hormones T4 and T3. T4 and T3 then travel through the bloodstream and regulate the function of various organs and metabolic processes within in your body. Some T4 is converted to T3 after leaving the thyroid.

Figure 2 - Function of the pituitary gland

What about iodine?

Iodine, an element found in food and water, is essential for the thyroid gland to produce thyroid hormones. Iodine deficiency is a cause of hypothyroidism, but varies in prevalence depending on geographic regions. For example, in North America and Europe, iodine deficiency is extremely rare because iodine is routinely added to salt. However, for people living in underdeveloped countries this is not the case, so iodine deficiency becomes a threat.

Is thyroid disease hereditary?

If a close relative has either an overactive or an underactive thyroid, then you are at increased risk for developing thyroid disease. Often, one relative will have an overactive thyroid and the next will have an underactive thyroid. This is not something that should be worrisome, however, as most people who have relatives with thyroid disease will not develop thyroid disease themselves. Despite the family history and the resultant increased risk, the vast majority will still not get thyroid disease.

Richard Bebb, MD 
in association with the MediResource Clinical Team

Thyroid nodules: what are they?

Many of the lumps that appear in the front or "anterior" aspect of the neck originate in the thyroid. Finding a lump in your neck is a frightening event and your immediate thoughts may be of cancer. However, the vast majority of thyroid lumps are in fact "benign" - or not cancerous.

How common are thyroid nodules?

A "nodule" is an enlarged area or "lump" of tissue. Thyroid nodules are surprisingly common. How common depends on how hard one looks for them, and your age. Trained physicians may find nodules in 4% Figure 1 - Frequency of thyroid nodules relative to the age of the patient. of women age 40 years and up, simply by feeling for lumps with their hands. If an ultrasound machine is used to examine those same women, as many as 40% of them may have small thyroid nodules. Fortunately, the vast majority of these small nodules are not of any clinical importance. However, exceptions to this rule would include people who have been exposed to radiation as children or people with family histories of thyroid cancer.

What should I do when I find a lump in my neck?

First and foremost do not panic - usually the lumps are not cancerous. However, do not ignore the lump or delay in seeing your doctor. If the lump is in the thyroid, your doctor will usually recommend a fine needle aspiration biopsy (FNAB) and a thyroid stimulating hormone level (TSH) test as the initial investigations. A referral to an endocrinologist or another specialist experienced in thyroid disease may also be necessary. If the FNAB yields a benign result, and the TSH is normal, further investigations are probably not necessary.

The decision to remove a benign nodule is entirely personal. If you think the lump is large enough to be of cosmetic concern, in some cases that may be reason enough to proceed with its surgical removal.

Dr. Richard Bebb, MD 
in association with the MediResource Clinical Team 

Thyroid nodules: detection

Tests for thyroid nodules include ultrasound examinations, radioactive iodine scans, and fine needle aspiration biopsies (FNAB). The FNAB is the most definitive test and should be the first one performed.

What is a fine needle aspiration biopsy (FNAB) of the thyroid?

This is the most important test used to assess the cause of an enlargement or lump in the thyroid gland. A small needle is placed into the thyroid and a microscopic amount of thyroid tissue is obtained in the needle tip. Many physicians will attach the needle to a special syringe so tissue can be "aspirated" or "sucked" back into the needle. The small sample of tissue is then taken to a hospital pathologist - a physician specializing in tissue specimens - for interpretation.

Sometimes the FNAB procedure is done in conjunction with an ultrasound examination, but usually it is done as a brief office procedure that does not require any painkillers. The degree of discomfort is similar to having your blood drawn for routine blood tests. The procedure of FNAB, especially the interpretation of the thyroid specimen, requires physicians trained and experienced in this technique.

What can a fine needle aspiration biopsy determine?

A fine needle aspiration biopsy generally leads to one of four different results. The results of the FNAB help determine the next step in investigation or the therapy required.

Benign nodule Benign thyroid nodules can either be observed or suppressed by taking thyroid hormone pills.
Suspicious for thyroid cancer Suspicious biopsy results require close follow-up with additional testing and often a repeat fine needle biopsy. Although many of these cases turn out to be a thyroid cancer, many are ultimately proven to be benign.
Thyroid cancer Thyroid cancers should be removed by surgery.
Insufficient biopsy: either not enough tissue was obtained or the sample was not sufficient to allow an exact diagnosis. Insufficient biopsies need to be repeated in order to obtain a better sample of tissue with which a pathologist can provide an exact diagnosis.


Flow-chart for findeneedle aspiration biopsy

What is an ultrasound examination?

Ultrasound is a way of scanning the human body using sound waves. It is painless, uses no radiation and is relatively fast to perform. Sound waves are sent into the body and an image of body tissues is created by analyzing how the sound waves "bounce off" body structures. Because no radiation is used, thyroid ultrasound examinations are safe during pregnancy.

What is a radioactive iodine uptake and scan test?

This test is available in the nuclear medicine department of most major hospitals. A small dose of radioactive iodine is taken orally and will show how metabolically active the thyroid tissue is.

The iodine is temporarily absorbed by the thyroid gland. The patient lies under a special scanner that detects any radioactivity given off by the iodine. Radioactive iodine is tasteless and painless to take, and although the dose of radiation is considered very low and safe to take, this test should not be performed on pregnant women or mothers who are breast-feeding.

Dr. Richard Bebb, MD 
in association with the MediResource Clinical Team 

Thyroid nodules: treatment

Suppression with thyroid hormone

The thyroid gland produces thyroxine (T4) and triiodothyronine (T3) as its major hormones. Thyroid hormone suppression is achieved by taking thyroid hormone (usually in the form of T4) in a dose slightly higher than what would normally be produced by your thyroid gland. This results in a suppression of the blood level of the thyroid stimulating hormone (TSH). When the TSH level is "suppressed," thyroid nodules will sometimes become smaller. This suppression can be used to help differentiate benign from cancerous thyroid nodules, decrease the size of a nodule for cosmetic reasons or as an attempt to avoid thyroid surgery.

What if I was exposed to radiation as a child?

Unfortunately, some people have been exposed to radiation as children, either through environmental disasters such as Chernobyl or through the use of medical radiotherapy to the head and neck area. Depending on the dose of radiation, there could be an increased lifetime risk of thyroid cancer. If you are having an assessment of a thyroid nodule, let your physician know if have been exposed to radiation.

The radiation from diagnostic X-rays such as those used by your dentist or during a routine chest X-ray does not increase your risk of thyroid cancer.

What if I find out I have thyroid cancer?

If your fine needle aspiration biopsy (FNAB) suggests thyroid cancer, your physician will refer you to a surgeon experienced in thyroid surgery. With few exceptions, the best course of action is the complete removal of the thyroid for several reasons:

  1. It ensures removal of any other thyroid cancers, and some people will have more than one.
  2. It allows for more treatment options after surgery to prevent the cancer recurring.
  3. If the entire thyroid is removed at the time of initial diagnosis, determining a reoccurrence of cancer becomes easier. There is no advantage to leaving part of the thyroid behind, as most people with thyroid cancer will be on lifelong suppression therapy with thyroid hormone.

The prognosis for properly diagnosed and treated thyroid cancer is excellent. Less than 10% of all patients with thyroid cancer die from this disease, and most are cured. Treatment always includes the initial surgery and usually long-term suppression therapy with thyroid hormone. Depending on the size and type of thyroid cancer, many patients will be treated with high dose radioactive iodine after surgery as this not only decreases the recurrence rate but also may increase the survival rate.

Potential treatment options for thyroid cancer

  • thyroidectomy (surgical removal of the thyroid)
  • suppression therapy with thyroid hormone
  • high dose radioactive iodine after surgery
  • external beam radiation
  • chemotherapy

  Dr. Richard Bebb, MD 
in association with the MediResource Clinical Team