Thyroid gland: facts, function & diseases


THE thyroid gland is a small, butterfly-shaped organ in your throat, and it is very important to your health and well-being. The thyroid is part of the endocrine system, which is essentially a collection of glands. Glands produce hormones that regulate mood and various functions in the body.
“Thyroid hormones impact a host of vital body functions, including heart rate, skin maintenance, growth, temperature regulation, fertility and digestion,” said Dr. Jerome M. Hershman, a professor of medicine at the David Geffen School of Medicine at UCLA and author of the thyroid sections of the Merck Manual.
The thyroid gland is 2 inches (5 centimeters) wide and it weighs between 20 and 60 grams (0.7 to 2.1 ounces), according to the U.S. National Library of Medicine. The gland stretches across the front of the neck, below the voice box. Like a butterfly, it has two wings called lobes that stretch around the windpipe. The wings are connected by a small piece called the isthmus.
The thyroid gland, in particular, controls just about every cell in the human body. It secretes hormones calcitonin, T4 (thyroxine, or tetraiodothyronine) and T3 (triiodothyronine) into the bloodstream. The hormones control the rate at which cells and organs turn nutrients into energy and the amount of oxygen cells use.
“In this way, the thyroid gland is the body’s master metabolic control center,” said Cindy Samet, a chemistry professor at Dickinson College in Carlisle, Pennsylvania. “Brain, heart and kidney function, as well as body temperature, growth and muscle strength — and much more — are at the mercy of thyroid function.”
The thyroid also regulates the brain and nerve function and development, plus the function of the skin, hair, eyes, heart and intestines.
The thyroid works in conjunction with the pituitary gland. The pituitary gland regulates how much hormones the thyroid releases. The thyroid gland produces a large amount of T4, but that hormone is not very active. T4 is converted to T3 via an enzyme that removes one of its iodine atoms. “Although T3 is much more potent than T4, there is much evidence to support that people with hypothyroidism feel much better when they receive a combination treatment that includes a small amount of T3 with the commonly prescribed T4,” Samet said.
Thyroid conditions affect an estimated 20 million Americans, and as many as 60 percent of people with a thyroid disease don’t know they have a problem, according to the American Thyroid Association.

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