Thyroid Gland Overview

A Major Player in Regulating Your Metabolism

Written by Robert M. Sargis MD, PhD

Thyroid Essentials

 
The thyroid’s main role in the endocrine system is to regulate your metabolism, which is your body’s ability to break down food and convert it to energy. Food essentially fuels our bodies, and our bodies each “burn” that fuel at different rates. This is why you often hear about some people having “fast” metabolism and others having “slow” metabolism.
 
 
The thyroid keeps your metabolism under control through the action of thyroid hormone, which it makes by extracting iodine from the blood and incorporating it into thyroid hormones. Thyroid cells are unique in that they are highly specialized to absorb and use iodine. Every other cell depends on the thyroid to manage its metabolism.
 
The pituitary gland and hypothalamus both control the thyroid. When thyroid hormone levels drop too low, the hypothalamus secretes TSH Releasing Hormone (TRH), which alerts the pituitary to produce thyroid stimulating hormone (TSH). The thyroid responds to this chain of events by producing more hormones. To learn more, read our article about how the thyroid works.
 
Anatomy of the Thyroid
Derived from the Greek word meaning shield, the thyroid is a butterfly-shaped gland located in front of the windpipe (called the trachea) and just below the larynx or Adam’s apple in the neck. It is comprised of two halves, known as lobes, which are attached by a band of thyroid tissue called the isthmus.
 
During development, the thyroid is actually located in the back of the tongue and has to migrate to the front of the neck before birth. There are rare instances when the thyroid migrates too far or too little. There are even cases when the thyroid remains in the back of the tongue—this is known as lingual thyroid.
 
Hormones of the Thyroid
The two main hormones the thyroid produces and releases are T3 (tri-iodothyronine) and T4 (thyroxine). A thyroid that is functioning normally produces approximately 80% T4 and about 20% T3, though T3 is the stronger of the pair.
 
To a lesser extent, the thyroid also produces calcitonin, which helps control blood calcium levels.
 
Diseases and Disorders of the Thyroid
There are many diseases and disorders associated with the thyroid. They can develop at any age and can result from a variety of causes—injury, disease, or dietary deficiency, for instance. But in most cases, they can be traced to the following problems:
 
Below are some of the most common thyroid disorders. To learn more, read our article about common thyroid problems.

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