The thyroid is a small, butterfly shaped gland located at the front of the neck. The thyroid produces the thyroid hormones, including the two major ones, namely the tri-iodothyronine (T3) and thyroxine (T4), which are essential for regulating the metabolic activities, growth, and several other body functions.

The thyroid gland is divided into two halves or lobes, and is connected by a thin 'bridge' of thyroid tissue known as the isthmus. The thyroid is usually larger in women in comparison to men.

The pituitary gland, which is situated at the bottom of the brain, and produces the thyroid-stimulating hormone (TSH), controls the functioning of the thyroid. TSH activates the thyroid to produce more thyroid hormones. Noted among the most widespread medical conditions, diseases of the thyroid gland are very common and affect millions of Americans. Thyroid disease occurs when the thyroid doesn't supply sufficient hormones required by the body to carry out its various functions properly. As the symptoms of thyroid are often noticed over a period of time, they are usually misdiagnosed.

The three most common thyroid problems are the underactive thyroid, the overactive thyroid, and thyroid nodules. Overactive thyroid releases excessive thyroid hormone into the bloodstream, resulting in hyperthyroidism. Hyperthyroidism causes the body to use up energy more rapidly than it should, and chemical activities in the cells such as metabolism speeds up. In the case of underactive thyroid, the thyroid gland is attacked by the body's immune system. Thyroid Nodules is a condition that begins as a small swelling or lumps in the thyroid gland. Other thyroid problems include inflammation of the thyroid gland, enlargement of the thyroid gland, and thyroid cancer.

In recent years, thyroid function tests have progressed significantly, allowing for diagnosis at an early stage, and better recovery rates than in the past.