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What is Thyroid Gland?

5 January 2023 | 21 mins read | What is Thyroid Gland?

What is Thyroid Gland?

The thyroid is a butterfly-shaped gland located in the front of the neck. Its main function is to produce and release two hormones which control the speed of metabolism.  

A few examples of processes affected by our metabolism include:  

  • Digestion. 
  • Blood circulation. 
  • Respiration. 
  • Transportation of oxygen and nutrients around the body. 
  • Healing.  
  • Sweating or shivering. 
  • Growing hair and nails. 

The two hormones produced by the thyroid gland are called “T3” (triiodothyronine) and “T4” (thyroxine).  

 

How does the thyroid know how much T3 and T4 to release?  

T3 and T4 levels continually rise and fall within a narrow range.  The way the body maintains thyroid hormone levels within this range is through the hypothalamus-pituitary-thyroid axis feedback loop.  

  • The process begins in a gland called the hypothalamus. The hypothalamus produces Thyrotropin Releasing Hormone.  (“TRH”).   
  • TRH tells a second gland called the pituitary gland to release a hormone called Thyroid Stimulating Hormone (“TSH”) 
  • TSH stimulates the third gland, the thyroid, to release T3 and T4.  
  • T3 and T4 travel throughout the body helping to regulate our metabolism.  
  • When the hypothalamus detects a certain amount of T3 and T4 it stops releasing TRH. In turn, the pituitary stops releasing TSH. The lack of TSH means that the thyroid isn’t stimulated to release T3 or T4.    
  • When the hypothalamus detects the lack of T3 and T4 it releases TSH, and the cycle begins again.  

 

What is hypothyroidism?

Hypothyroidism means that the thyroid is producing too little thyroid hormone.   

The decreased level of thyroid hormone causes the body’s metabolism to slow down. This causes symptoms such as:  

  • Weight gain. 
  • Slower heart rate.
  • Fatigue. 
  • Slowed speech. 
  • Puffy eyes and/or face. 
  • Droopy eyelids. 
  • Hoarseness. 
  • Constipation 
  • Dry hair and/or skin. 
  • Constantly feeling cold
  • Carpal tunnel syndrome. 
  • Elevated cholesterol. 

Affected children and teenagers are vulnerable to additional consequences of hypothyroidism, including short stature and delayed puberty. 

 

What is hyperthyroidism? 

Hyperthyroidism means that the thyroid is producing too much thyroid hormone. 

The increased level of thyroid hormone causes the body’s metabolism to speed up.  This causes symptoms such as:  

  • Abnormal heart rhythms. 
  • Fast heartbeat. 
  • Tremors. 
  • High blood pressure. 
  • Increased sweating. 
  • Anxiety. 
  • Insomnia. 
  • More frequent bowel movements. 
  • Unintentional weight loss.

 

How are hypothyroidism and hyperthyroidism diagnosed?  

If you have symptoms of thyroid disease your health care practitioner is likely to recommend one or more blood tests known as thyroid function tests.  For more information, see LINK HERE.   

What are the most common causes of hypothyroidism? 

The most common cause of hypothyroidism is an autoimmune condition called Hashimoto disease (also known as Hashimoto thyroiditis or chronic lymphocytic thyroiditis).  

Our immune systems make antibodies to attack harmful outside invaders such as viruses or dangerous bacteria.  In Hashimoto disease, the immune system makes antibodies that target and destroy healthy thyroid tissue. As a result, the thyroid can’t produce enough thyroid hormone. 

Other causes include: 

  • Surgery involving the thyroid. 
  • Radiation directed to the head, neck, or chest area. 
  • Iodine deficiency or excess. 

  • Medications, particularly lithium, amiodarone, and some anti-cancer drugs 
  • Treatment for Graves disease.
     

What are the most common causes of hyperthyroidism? 

The most common reason for hyperthyroidism is another autoimmune condition, called Graves disease.  

In Graves disease, rather than destroy thyroid tissue, the antibodies stimulate the thyroid to overproduce thyroid hormone.   

In addition to symptoms of hyperthyroidism, severe cases of Graves disease can cause vision and eye problems, including an outward- bulging appearance of the eyes. 

Graves disease occurs in both men and women of any age but is most often first diagnosed in women between 20 and 40 years old.  

Another common cause of hyperthyroidism is a nodule – a growth or lump in the thyroid that overproduces thyroid hormone. Thyroid nodules are extremely common, often unnoticed, and are usually harmless.  However, if the nodule causes symptoms or is seen on an imaging test, your doctor will most likely recommend further tests. 

Another cause is inflammation of the thyroid.  Inflammation of the thyroid is called ‘thyroiditis’.  Causes of thyroiditis can include:  

  • Exposure to certain viruses or bacteria. 
  • Exposure to certain toxic environmental substances. 
  • Exposure to certain medications. 
  • Taking too much medication prescribed for an under-active thyroid.   
  • Recent pregnancy.   

This form of thyroiditis is called ‘Postpartum Thyroiditis’ because symptoms typically develop several months after delivery.  However, women who develop it may have had an undetected autoimmune condition during or prior to pregnancy.

 

What are the risk factors for developing an autoimmune thyroid disease? 

Risk factors for autoimmune thyroid disease include:  

  • Being female, especially if pregnant, recently pregnant, or over the age of 60. 
  • Having family members with a history of thyroid disease. 
  • Having an autoimmune condition or having a close relative with an autoimmune condition, especially any of the following:
    -Type 1 diabetes
    -Celiac disease
    -Arthritic diseases
    -Systemic Lupus Erythematosus
    -Sjogren syndrome
    -Vitiligo

 

  • In combination with a family history of autoimmune conditions or genetic predisposition to autoimmune thyroid disease, environmental factors such as:
    -Exposure to radiation
    -Too much or too little intake of iodine
    -Exposure to certain chemicals 

The thyroid is a little gland with a lot of responsibility.  We don’t have much control over some of our risk factors for developing thyroid disease.  However, getting regular check-ups, eating a healthy diet, and getting plenty of exercise and sleep, will benefit not only your thyroid but your entire body.