Thyroid Disease Causes, Types, Symptoms, and Treatment on MedicineNet.com

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Thyroid Disease

Medical Author: Ruchi Mathur, MD
Medical Editor: William C. Shiel, Jr., MD, FACP, FACR

Featured thyroid disease patient discussions on experience

"I have been suffering from thyroid nodules my entire life but my thyroid blood work was always normal. I had biopsies performed because I was choking and the nodules could be seen protruding from my throat. The biopsy was benign and I underwent radioactive treatment to shrink the nodules. I have gained so much weight, dry skin, constipated, trouble sleeping, osteoporosis, and restless legs. My doctor won't increase my Synthroid because my blood work is normal. i am almost an anorexic ,desperate to lose weight( I am about 50 pounds overweight eating a 1000 calorie diet, exercising three times a week. "

"i just found out i have hypo thyroid and now i am having trouble with my eyes floaters, flashes scary do not want to go blind. pains in my chest down my arm "

"I often complained of being tired and cold, but my doctor could not find my problem until I found out that hypothyroid problems run in my family. I was tested and found my TSH was extremely high. I was put on medication until my basil body temperature was normal. When I was forced to change doctors my new doctor did not go by basal body temp. He only went by the TSH results and lowered my meds three times. I still feel OK except I am extremely cold now and my hands often turn blue and some of my fingers turn white and hurt. I have complained of being cold, but my doc said my TSH is in the normal range."

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Top Searched Thyroid Disease Terms:

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Patient Discussions are not a substitute for professional medical advice, or treatment.
See the disclaimer at the bottom of the comments page.

Introduction to thyroid disease

When I was asked to write an article on "thyroid disease", I took a very deep breath. The task seemed daunting. As any Endocrinologist (hormone specialist) knows, there are many subtopics within this giant topic, and an article like this could go on for a hundred pages! So, once I caught my breath, I decided to simply design this article to present a "rough guide" to the thyroid. This article will be an outline or introduction to many conditions that involve the thyroid gland. As you read through this, you will find a number of links that will take you to more in-depth articles dealing with the specific topic in question.

Thyroid 101: What is the thyroid and what does it do?

The thyroid is a butterfly-shaped gland located in the front of the neck just below the Adams apple. The gland wraps around the windpipe (trachea) and has a shape that is similar to a butterfly formed by two wings (lobes) and attached by a middle part (isthmus). The thyroid gland works like a tiny factory that uses iodine (mostly from the diet in foods such as seafood and salt) to produce thyroid hormones. These hormones help to regulate the body's metabolism and effects processes, such as growth and other important functions of the body.

The two most important thyroid hormones are thyroxine (T4) and triiodothyronine (T3), representing 99.9% and 0.1% of thyroid hormones respectively. The hormone with the most biological power is actually T3. Once released from the thyroid gland into the blood, a large amount of T4 is converted to T3 - the active hormone that affects the metabolism of cells throughout our body.

Picture of the thyroid gland

Thyroid hormone regulation - the chain of command

The thyroid itself is regulated by another gland located in the brain, called the pituitary. In turn, the pituitary is regulated in part by the thyroid (via a "feedback" effect of thyroid hormone on the pituitary gland) and by another gland called the hypothalamus.

Picture of the pituitary gland

The hypothalamus releases a hormone called thyrotropin releasing hormone (TRH), which sends a signal to the pituitary to release thyroid stimulating hormone (TSH). In turn, TSH sends a signal to the thyroid to release thyroid hormones. If overactivity of any of these three glands occurs, an excessive amount of thyroid hormones can be produced, thereby resulting in hyperthyroidism. Similarly, if underactivity of any of these glands occurs, a deficiency of thyroid hormones can result, causing hypothyroidism.

Hypothalamus - TRH

Pituitary- TSH

Thyroid - T4 and T3

The rate of thyroid hormone production is controlled by the pituitary gland. If there is an insufficient amount of thyroid hormone circulating in the body to allow for normal functioning, the release of TSH is increased by the pituitary in an attempt to stimulate more thyroid hormone production. In contrast, when there is an excessive amount of circulating thyroid hormone, TSH levels fall as the pituitary attempts to decrease the production of thyroid hormone.

There is another hormone that is produced by the thyroid called calcitonin. Calcitonin is produced by specific cells in the thyroid gland, and unlike T3 and T4, it is not involved in this regulation of metabolism. Calcitonin is a hormone that contributes to the regulation of calcium and helps to lower calcium levels in the blood. Excess calcium in the blood is referred to as hypercalcemia.