Thyroid disorders

The thyroid gland is located in the front of the neck and produces thyroid hormone, which helps regulate the body’s metabolism. Problems with the thyroid gland include too much (hyperthyroidism) or too little (hypothyroidism) thyroid hormone, inflammation of the thyroid gland (thyroiditis), thyroid nodules (lumps in the thyroid gland), or thyroid cancer.

Hyperthyroidism refers to having too much thyroid hormone in the blood, which results in an increase in the body's metabolism. Symptoms can include feeling warm, increased perspiration, heart palpitations, shakiness, weight loss, and hair loss, but sometimes people can just feel tired and weak. Hyperthyroidism is diagnosed by blood tests. Sometimes a thyroid scan is needed to determine the cause.

The most common cause of hyperthyroidism is "Graves' disease"; an autoimmune condition in which antibodies in the blood stimulate the thyroid gland to produce too much thyroid hormone. This condition requires treatment with medication to slow the thyroid gland. Graves' disease can sometimes go into remission (become inactive) after treatment, but it usually recurs after a period of time. People who do not have a remission of Graves' disease may need permanent treatment, such as radioactive iodine therapy, which usually results in permanently low thyroid function, requiring lifelong thyroid hormone replacement.

Another major cause of hyperthyroidism is an inflammation of the thyroid gland called "thyroiditis". This condition comes in several forms and is discussed below. There are several, less common causes of hyperthyroidism, which are not discussed here.

Hypothyroidism refers to having too little thyroid hormone, which can result in a slowing of the body's metabolism. The most common cause is from immune destruction of the thyroid gland (Hashimoto's thyroiditis - see below for more details). Other causes include radioactive iodine treatment, surgical removal of the thyroid gland, radiation treatments of the head and neck and certain medications. Symptoms of hypothyroidism can include tiredness, feeling cold, weight gain, dry skin, constipation, and swelling (edema) of the face or ankles. These symptoms can be very gradual and general (non-specific) and may not be recognized at first. Hypothyroidism is diagnosed by a blood test (TSH), which can be done by your family doctor. Sometimes, other blood tests (T4 and T3) may be ordered, but are often not essential to make the diagnosis.

Hypothyroidism can sometimes be temporary, but is often permanent and requires lifelong thyroid hormone replacement. The most common recommended treatment uses levothyroxine (T4), in the form of a daily pill, which is stable, long-acting, and effective. Other forms of thyroid hormone (e.g. combination T4 and T3, or desiccated animal thyroid hormone) may also be used, but may be difficult to achieve a stable level of hormone in the blood.

Thyroiditis refers to inflammation of the thyroid gland. This can sometimes result in a temporary increase thyroid hormone in the blood (hyperthyroidism), but can also cause long-term destruction of the thyroid gland, eventually causing low thyroid hormone (hypothyroidism).

The most common form of thyroiditis is called "Hashimoto's thyroiditis", which is a long-term, autoimmune condition, often resulting gradual damage to the thyroid gland and permanently low thyroid hormone levels. The diagnosis usually is made by testing for the thyroid peroxidase (TPO) antibody in the blood. Currently, there is no way of preventing the loss of thyroid function, so if the thyroid levels fall below normal, long-term thyroid hormone replacement is the only option for treatment.

Other forms of thyroiditis include "Painless" (Silent), "Post-partum" or "Painful" (Subacute), as well as other less common forms. Each of these conditions can result in a temporary increase in thyroid hormone (hyperthyroidism), which can last several months. However, these episodes are usually self-limited and the thyroid function returns to normal. Sometimes, the gland is so damaged that it never returns to normal, resulting in permanent hypothyroidism, requiring lifelong thyroid hormone replacement.

The thyroid gland often develops nodules (lumps) within the gland. Nodules are common and tend to increase with age. Most of these nodules are benign (non-cancerous) and usually do not cause problems, but about 5-10% may be cancerous. Nodules are usually detected by ultrasound, or can sometimes be large enough to feel. To determine whether a nodule is cancerous can require a fine-needle aspiration (biopsy), but this is only necessary for nodules greater than 1.0-1.5 cm in diameter or which have unusual features on ultrasound,

If a nodule is benign, no treatment is usually needed. However, if a nodule grows large enough, it can sometimes cause symptoms, such as pressure in the neck, hoarseness of the voice, or difficulty swallowing or breathing. If this occurs, then the nodule can be removed by surgery. Currently, no medication can reliably shrink a thyroid nodule.

If a thyroid nodule is determined to be cancerous, it must be surgically removed. Details about thyroid cancer are contained below.

Thyroid cancer is the 5th most common cancer in women and the 16th most common cancer in men. It is highly treatable and rarely causes death. The two most common forms are "papillary" and "follicular" cancer. These forms of thyroid cancer are usually low grade and do not spread quickly. Less common forms of thyroid cancer include medullary (which tends to run in families), anaplastic, or thyroid lymphoma, which may be more aggressive, but are quite rare.

The diagnosis of thyroid cancer is usually made by fine-needle aspiration (FNA) of a thyroid nodule. Thyroid cancer is treated by surgical removal, but sometimes requires additional treatment with radioactive iodine. The best course of treatment for thyroid cancer should be determine by a thyroid cancer specialist (endocrinologist, oncologist or head & neck surgeon).

For more information about thyroid disease, please see the Endocrine Links section.