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What exactly does a thyroid do?

By Tanya Munshi
Last updated on: March 08, 2007 11:18 IST
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Not many are sure what the thyroid does in the human body.

Some associate it with a disease. Dr Caesar Sengupta, MD, Senior Manager Processing of Thyrocare Technologies (a thyroid testing laboratory) clarifies:"It is not a disease, but a gland, and an integral part of the body."

The thyroid is a small, butterfly-shaped gland located in the base of our neck, just below the Adam's apple. The two main hormones produced by it are iodine (containing hormones Thyroxine or T4) and Triiodothyronine (or T3) that circulate in the body through the bloodstream and work on every living tissue and cell. TSH, a thyroid-stimulating hormone, is produced by the pituitary that stimulates the thyroid gland. "These hormones are essential for life and have many effects on body metabolism, growth and development. For example, thyroid hormones make the heart beat faster and cause the body to burn up calories more quickly," says Dr Sengupta.

Thyroid levels

The normal or healthy range for T3, T4 and TSH will vary slightly from laboratory to laboratory, depending upon the kind of tests, brand of reagents and analysers used for the measurement of the hormones.
According to Thyrocare, the values are:

Triiodothyronine (T3): 60-200 ng/dL

Thyroxine (T4): 4.5-12 µg/dL

Thyroid stimulating Hormone (TSH): 0.30-5.50 µ IU/ml

When you get your medical reports, this is what you will see. Any amount below or above the given range needs medical advice.
"But remember, no single laboratory test is 100 per cent accurate in diagnosing all types of thyroid disease. A combination of two or more tests can detect abnormality of thyroid function," adds Dr Sengupta. Treatment regimes for thyroid disorders are normally determined by regular blood tests and clinical observation.

Common thyroid conditions

"There are certain problems associated with thyroid, the most common among the general population being Hypothyroidism and Hyperthyroidism," adds Dr Sengupta. Hypothyroidism is a condition where the thyroid gland doesn't produce a sufficient amount of hormones (underactive thyroid), while it produces more (overactive thyroid) in the case of Hyperthyroidism.


The most common cause of this is Hashimoto's thyroiditis, an autoimmune condition that destroys the thyroid gland. Hashimoto's thyroiditis is an auto-immune disease where the body's own anti-bodies attack the thyroid cells. Auto-immunity occurs when an organism or body fails to recognize its own constituent parts, thereby turning against its own cells and tissues. It is a state where immune cells in your body mistake your own organs, cells or glands as intruders and attack them. "Auto-immunity can work against any organ. It could be auto-immunity of the stomach or joints, and when it acts on the thyroid gland, we call it auto-immune thyroiditis," explains Dr. Sengupta.

Hypothyroidism is found more often in women than men and can be missed in its early stages because of its very insidious onset with symptoms, which can simulate many other diseases. In the beginning of development of clinical hypothyroidism, even before the TSH level is high enough to warrant treatment, the body's metabolism can slow down. This means fewer calories burned each day, and even those few calories start to add up.

Hypothyroidism brings in lethargy, which makes regular exercise even more troublesome and the vicious cycle sets in. It occurs when the body's metabolism is too slow due to an absence or deficiency of the thyroid hormone. The good news is, it can be easily treated, as it requires a replacement of hormones through medication and the regular monitoring of blood levels of the hormones.


This occurs when an excess in thyroid hormone produces symptoms of abnormally high metabolism, either due to an overactive thyroid gland or taking too much thyroid hormone replacements – like medicines. The most common cause of hyperthyroidism is Graves' disease -- an auto-immune disease where the body's own immune system mistakenly attacks its own thyroid gland, causing it to overproduce the Thyroxine hormone.

There are three options for treatment namely: medical, surgical and radioactivity.

"An experienced and trained physician would be the best judge to offer the appropriate form of treatment especially if the problem is further complicated with pregnancy. Some of the symptoms in pregnancy also mimic those manifested with thyroid dysfunction," adds Dr Sengupta.

Tomorrow: Thyroid diseases and symptoms

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Tanya Munshi