What Does the Thyroid Do?

by admin on January 12, 2010

Your thyroid is a butterfly-shaped organ that lies across the cartilage of your neck above the collar bone. The role of the thyroid is to  stimule metabolism and along with the parathyroid glands ( beside or near thyroid), controls the body’s circulating calcium levels.

The thyroid produces T3 and T4; triiodothyronine and thyroxine for those of you who like wordy words as well as calcitonin. As their name suggests, both T3 and T4 use iodine, and their numbers refer to how many iodine molecules are attached to the structure. Detailed and easy to understand information about the thyroid is hard elusive and I find myself having to refer to my anatomy and physiology textbooks to provide the best answer. Your thyroid has two different kinds of follicle cells – cells that secrete hormones: follicular cells and parafollicular cells. Your follicular cells produce T3 and T4.

Your pituitary gland is located in your brain and secretes, among other things Thyroid Stimulating Hormone (if it is a stimulating hormone, it comes from your pituitary gland). TSH tells your thyroid to make T3 and T4 which travel to every cell in your body and stimulate those cells to produce protein or increase oxygen usage.

The thyroid’s parafollicular cells produce calcitonin which decreases the amount of circulating calcium in your blood. To help you remember this, think “calcitonin tones down the body’s calcium.” Your body does this by storing the excess calcium in your bones, and interestingly, calcitonin contributes to us no longer feeling hungry. There are times also, when you need to increase the amount of circulating calcium. The parathyroid glands that sit atop the thyroid secrete parathyroid hormone to stimulate our bone cells to release calcium, by stimulating our kidney to reabsorb calcium in the process of urine concentration, and stimulates our small intestine to absorb more calcium from the food we eat via Vitamin D. Essentially, the small intestine asks the kidney for a usable form of Vitamin D which enhances the absorption of calcium by the microvilli in your small intestine. The production of parathyroid hormone is not dependent upon a feedback loop with the pituitary gland in your brain. Sensors on the parathyroid gland themselves can measure the amount of circulating calcium in the blood.

There are lots of different disorders associated with the thyroid, but almost all of them break down into too little or too much thyroid hormone. The cause can be linked to a problem with the thyroid itself, or a problem with the hypothalamus or pituitary gland in your brain. Whatever the case, symptoms are similar.

Hypothyroidism is a deficiency of thyroid hormone. Although, as I stated, there are many causes, the most common cause is iodine insufficiency  (the introduction of iodized table salt into our collective diet has helped with this problem). Since T3 and T4 are responsible for cellular metabolism, our body doesn’t metabolize our food properly, nor does it get the boost in energy that increased oxygen production supplies; leading to weight gain, tiredness, cold intolerance, muscle cramps, joint pain, carpal tunnel syndrome,decreased sweating, brittle hair and nails , constipation and a low heart rate. Hashimoto’s thyroiditis is an autoimmune disorder that causes hypothyroidism, and ironically, the drug treatment for hypER thyroidism can cause hypothyroidism.

Hyperthyroidism in an excess of thyroid hormone that lead increases metabolism beyond a healthy level. This results in stimulating the body’s sympathetic nervous system (the getting ready for fight system fueled by adrenaline). This exhibits as fast heart beat, palpitations, tremor, anxiety, diarrhea and weight loss – not a good diet plan. Grave’s disease is the most common presentation of hyperthyroidism.

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