Understanding the thyroid gland

 Hypothyroidism, or an underactive thyroid gland, is the second most common disease of the endocrine system, behind diabetes. That being said, only about 5 percent of Americans will be diagnosed with the condition.  

The thyroid gland is normally located on the front of the neck and below the larynx or “Adam’s apple.” Thyroid literally means “shield-like,” describing its shape. It has two lobes that are attached at the front of the neck. The thyroid gland produces iodine-containing hormones, mainly T4 and T3. These hormones regulate the body’s general metabolic activity. They also affect another hormone – calcitonin – which controls calcium use by the body.  

The pituitary gland in the brain tells the thyroid to make more or less hormone depending on the blood levels of thyroid hormone. It is one of the body’s many feedback systems. The pituitary produces thyroid stimulating hormone (TSH); TSH stimulates the thyroid to make thyroid hormone, and thyroid hormone shuts off the pituitary production of TSH.    

If the thyroid gland is not able to produce enough hormones, the blood levels of TSH will go way up. This is because the pituitary is telling the thyroid to make more hormones, but it is not responding. A high TSH level in a blood sample helps to diagnose the disease.

There are many causes for an underactive thyroid. The most common is called Hashimoto’s thyroiditis and is the result of inflammation in the thyroid gland. It is thought to be an immune reaction of the body against itself. Another frequent cause is surgical removal or radiation of the thyroid due to other thyroid diseases (e.g. thyroid cancer or overactive thyroid).

Hypothyroidism is five to 10 times more common in women. There may be a genetic predisposition in some cases. It is usually seen in individuals over 40 years of age, and the incidence increases with advancing age.  

The symptoms of an underactive thyroid can be multiple and somewhat broad. This is because the thyroid affects the body’s general metabolism and most other organ systems. The most common symptoms are weakness, dry skin, lethargy, slowed speech, swelling of the extremities, feeling cold, thickness of the tongue, hair thinning or loss, weight gain, and constipation.      

 Some individuals may develop swelling of the thyroid gland. This is called a goiter. Others may sense a difficulty when swallowing due to an increased size of the gland. More prolonged cases of thyroid deficiency can lead to high cholesterol levels in the blood and heart rhythm disturbances, such as atrial fibrillation.  

Treatment of hypothyroidism is generally straight-forward. The deficient hormone is simply replaced by taking a daily thyroid hormone pill. Blood tests need to be done at regular intervals to monitor the TSH level. The dosage of the medicine is adjusted until the TSH is in the normal range. Treatment with thyroid hormone replacement is usually life-long, and regular doctor’s visits are required to periodically monitor symptoms and blood levels.   

The content in this column is for informational purposes only. Consult your physician for appropriate individual treatment. Dr. Reynolds practices Family Medicine in Chesterfield.

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