Goitre; Causes, Signs and Symptoms, Diagnosis and Treatment

Introduction

A goitre (latin = struma) also called a bronchocele, is a swelling in the neck (just below the larynx due to an enlarged thyroid gland.

Classification of Goitre

All grades of goitre are encountered, from those that are barely visible to those producing disfigurement.

Toxic goitre are accompanied by hyperthyroidism (over activity of the thyroid gland, resulting in a rapid heartbeat and an increased rate of metabolism). Non-toxic goitre however, are associated with a euthyroid state (normal functioning thyroid gland) or low thyroid levels. Endemic goitre refers to those that occur in a particular geographical region and from a common cause, such as iodine deficiency.

Goitre can also be classified into:

  1. Diffuse goitre is a goitre that has spread through the entire thyroid.
  2. Toxic goitre refers to goitre with hyperthyroidism. These are commonly due to Graves’ disease, but can be caused by inflammation.
  3. Non-toxic goitre – simple goitre (associated with low thyroid levels) refers to all other types such as that caused by an iodine deficiency. Simple goitre may also be caused by an intake of large quantities of goitrogenic substances. These substances include excessive amount of cabbage, cassava, carrot etc.

Causes of Goitre

There are different causes of goitre;

Worldwide, the most common cause for goitre is iodine deficiency; iodine found in fish products, drinking water, table salt etc. is essential for the production of thyroid hormone. If there is a lack of iodine, an individual will suffer from hypothyroidism. A fall in levels of thyroid hormones stimulates synthesis of the hormones. In an effort to produce more thyroid hormones, the thyroid gland is over stimulated and enlarges to form goitre.

In clinical terms, iodine is necessary for the synthesis of the thyroid hormones thyroxin (T4) and triidothyronine (T3). In goitre, iodine deficiency leaves the thyroid gland unable to produce its hormones because the hormones are made out of iodine. When levels of thyroid hormones fall, thyrotropin – releasing hormone (TRH) is produced by the hypothalamus.

TRH then prompts the pituitary gland to make thyrotrophic or thyroid stimulating hormone (TSH), which stimulates the thyroid’s production of T4 and T3.

Therefore in an effort to produce more thyroid hormones, the thyroid gland is over stimulated and enlarged to form goitre. This causes the thyroid gland to grow in size by increasing cell division.

Photo by News Medical
Other causes of goitre include:

  • Hashimoto's thyroiditis (chronic thyroiditis): This is an autoimmune disorder where the immune system destroys the thyroid gland which results in less thyroid hormones being produced. In other words, the circulating antibodies bind to the cells in the thyroid gland resulting in hypothyroidism. The pituitary gland then stimulated the thyroid gland to produce more hormones, causing it to enlarge and goitre can then develop.
  • Grave’s disease: This is an autoimmune disorder which causes the thyroid gland to be overactive (hyperthyroidism). Excessive output of thyroid hormones is thought to be due to abnormal stimulation of the thyroid gland by circulating immunoglobulin. In Graves’ disease, the antibodies produced by the immune system binds to specific cells in the thyroid gland and stimulates the gland to produce excessive amount of thyroid hormones causing enlargement, resulting in a goitre.
  • Acute thyroiditis; is usually the result of bacterial invasion of the thyroid. Evidence also indicates that this disorder may be caused by viral infection.
  • Ingestions of goitrogens, such as cabbages, carrots, cassava, soya beans etc. these foods contain goitrogens factors.
  • Thyroid cancer.
  • Chemical effect e.g. example is lithium.
  • Pregnancy: during the first trimester of pregnancy, a hormone called human chorionic gonadotropin (HCG) can result in an enlarged thyroid gland. The thyroid gland mistakenly registers HCG for TSH (Thyroid stimulating hormone) produced by the pituitary gland and enlarged in response to it.

Signs and symptoms

  1. Mainly the swelling of the neck.
  2. Abnormal protrusion of the eye balls (exophthalmos) results from the accumulation of fat deposits behinds the eye and inflammation of the extraocular muscles. The accumulating pressure forces the eyes outward from their orbits. This usually occurs in Grave’s disease.
  3. Goitre puts pressure on other part of the neck such as the trachea and oesophagus making it difficult to breathe and causing swallow breaths.
  4. Coughing.
  5. A feeling of tightness in the throat.
  6. Changes in voice (hoarseness of voice).
  7. Emotional upsets.
  8. Depression.
  9. Weeping etc.

Diagnosing Goitre

The presence of an enlarged thyroid (goitre) indicates there is a problem with the thyroid gland, even if the patients do not have any clinical signs of a thyroid problem.

Diagnostic test to confirm goitre

  1. Hormone test; blood test measuring all the various thyroid hormones will help to determine how the thyroid is functioning. If the thyroid is overactive, the level of thyroid hormone (T3 and T4) in the blood will be high.
  2. Antibody test: a blood test may confirm the presence of antibodies.
  3. Ultrasonography: an ultrasound scan is an imaging test that will be able to reveal the size and shape of the gland and the presence of any nodules.
  4. Thyroid scan: this will help evaluate the structure and function of the thyroid and involves the administration of radioactive substance.
  5. Thyroid biopsy: thyroid tissue for biopsy is obtained through surgical excision with the patient under general anaesthesia.

Treatment of Goitre

Treatment of goitre depends on a number of factors. Once these factors are determined plan of treatment can begin. They are;

  1. Symptoms
  2. Underlying cause
  3. Size of the enlargement; Treatment may not be necessary if the goitre is small.

Conventional goitre remedy often involves:

  • Observation
  • Medical Management

Prescription of ‘anti-thyroid’ medication such as; Methimazole (Tapazole), Propylthiouracil (PTU), Propranolol (inderal), Levothroxine, Iodine 131 is usually necessary.

Some of these drugs decrease thyroid hormones synthesis, thus they decrease the circulating thyroid hormone levels and decrease their formation. They are prescribed in fairly high doses. Examples are Methimazole (Tapazole), Propylthiouracil (PTU). PTU also blocks the conversion of T4 hormones to the more metabolically active T3 hormone.

To inhibit thyroid hormone release from the thyroid gland Lugols’ solution can be given. Beta blockers such as propranolol (Inderal) can help to control heart rate while Levothroxine is used to treat hypothyroidism.

Iodine 131, a radioactive isotope of iodine is given orally either by pill or liquid. This is usually important for goitre patients who do not respond to levothyroxine treatment, especially if the patient has difficulty in breathing or swallowing. It can relieve obstruction and reduce the size of the goitre by 30-65%.

Note: Radioactive iodine treatment and surgery are usually used as a last resort.

  • Surgical intervention

Total thyroidectomy is rarely indicated but it is performed to treat cancer of the thyroid, the client then requires life-long hormone replacement.

Depending on how large the goitre is and how much of the thyroid gland must be removed or destroyed, thyroidectomy may produce hypothyroidism requiring life-long treatment. An anti-thyroid drug is used before surgery to induce euthyriod (normal thyroid state) in order to reduce the size and vascularity of the gland thereby decreasing the risk of hemorrhagic. The goal in the thyroidectomy is therefore to remove the thyroid tissue which is producing the excessive thyroid hormone.

A subtotal thyroidectomy is usually performed. This procedure leaves enough of the gland in place to produce an adequate amount of thyroid hormone.

Complication of thyroidectomy

  • Hemorrhage, oedema of the glottis (the part of the larynx consisting of the vocal cords and the slit-like opening between them) and injury to the laryngeal nerve may occur.
  • Parathyroid gland may be injured or removed, producing disturbances of the calcium metabolism of the body.
  • Respiratory distress may also occur.

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