Thyroid Disorders -Goiter

What is a goiter?

A goiter is an enlarged thyroid gland.   A normal gland weighing ~1/2 oz can increase up to ~2 pounds. The whole gland can enlarge (called diffuse goiter) or there can be one or more small nodules. Enlargement is not due to physical inflammation, but is a thick tissue growth caused by the presence of chronic or agressive thyroid stimulating hormone (TSH); this may occur for a variety of reasons, including, for example,  iodine deficiency, pregnancy, inflammatory thyroid damage or having diagnosed (or undiagnosed) Hashimoto's thyroiditis.

Most nodules (lumps) are cysts filled with fluid, called cystic nodules); nodules can also contain the stored form of thyroid hormones, collectively called colloid; solid nodules have minimal fluid or colloid.

A goiter can be associated with:

• Hyperthroidism / An overactive thyroid  / Excessive thyroid hormones
• Hypothroidism /An underactive thyroid  /  Insufficient thyroid hormones
• Normal thyroid hormone levels

Physical characteristics of a goiter can be:

• Symmetrical  or Nodules or enlargement are in just one part of the gland
• Diffuse (spread out, generalized, smooth, as in Grave's disease) or solitary (if only a small area is enlarged; commonly benign cysts, nodules)
• Nodules are benign or malignant (cells in nodule have the ability to spread outside the thyroid gland)

Non-toxic, toxic or endemic goiter?

Non-toxic Goiter

• Diffuse (spread out) or Nodular (i.e. lumps; 1 = solitary thyroid nodule / more than 1 = multinodular goiter)
• Thyroid hormone production is normal
• Non-cancerous
• Not associated with Hyperthroidism,  Hypothyroidism, or inflammation

Toxic DIFFUSE or NODULAR Goiter

• Diffuse Toxic Goiter (a.k.a. Graves Disease or exophthalmic goiter)  (involves autoimmune-antibodies / auto-antibodies)   /  Toxic Nodular Goiter (not an autoimmune disease);
• Excessive secretion of thyroid hormones;
• Causes signs and symptoms of hyperthyroidism;

Endemic Goiter (Goitrous hyperthyroidism)

• Inability to make sufficient hormones;
• Associated with Hypothroidism

Symptoms

A goiter is seen as a swelling at the front base of the neck

The enlarged thryroid compresses the trachea (windpipe) and esophagus.    This can lead to such symptoms as:

• Coughing;
• Waking up with the feeling of being unable to breathe;
• Sensation of food stuck in upper throat

Causes 

A goiter could occur as a result of:

• Inadequate iodide levels.   This being the most common cause of goiter worldwide, particularly prevalent in areas of iodine-deficient soil; referred to as ENDEMIC goiter.
• Hashimoto's Thyroiditis.    An autoimmune thyroiditis; anti-thyroid antibodies attack thyroid causing damage/inflammation leading to hypothyroidism

• Ord's thyroiditis.    Seen particularly in Europe; an atrophic form of autoimmune thyroiditis;

•  Increase in thyroid stimulating hormone (TSH).   This is in response to a problem with usual/normal thyroid hormone production;   
• Malfunctioning/damaged/ inflamed thyroid.   Damage possibly results from insufficient  iodine intake;
• Excessive presence of goitrogens.   These can block thyroid access to iodine needed for TH production and create unused thyroglobulin (Tg);
• Hypothyroidism.    Since low hormone levels stimulate TH production;
• Some drugs.    Lithium inhibits release of TH; amiodarone may induce inflammatory damage to thyroid;
• Thyroid Cancers / Benign tumors (nodules).   May cause a multinodular goiter (solid or fluid-filled lumps, called nodules);
•  Pregnancy.   The pregnancy hormone human chorionic gonadotropin (HCG) may cause slight thyroid enlargement;
•  Graves Disease / Diffuse Toxic goiter.   Autoimmune disease stimulates thyroid to be overactive;
•  Too much iodine ???;  Currently researching this.

Risk Factors

Anyone from birth onwards can have goiters.   Some common risk factors are:

•  A lack of iodine
•  Being female / Pregnancy / Menopause
•  Age > 40
•  Family history of autoimmune disease
•  Radiation exposure.    Medical radiation to neck/chest area or general exposure from nuclear sources
•  Certain medications.    The heart drug amiodarone (e.g. Pacerone, Cordarone), lithium (e.g. Lithobid)

References

Marine D, Kimball BS. (1917) The prevention of simple goiter in man. J Lab Clin Med; 3:40-48.

Marine D. (1923) Prevention and treatment of simple goiter.  Atl Med J; 26:437-442.