A Lesson in Biology; Metabolism and the Thyroid
“I wish I had your metabolism!” says your mom as you devour your high Calorie pasta dish. What she means is I wish my body could burn Calories as fast as your body. Biochemically speaking, metabolism refers to any chemical reaction that is building or breaking down molecules within your cells. To maintain life requirements the average female adult human needs around 1450 Calories and male 1750. However, these averages are not specific to the differing metabolic rates of individuals. The simple answer for why we gain weight is because we eat more Calories than we spend. If thyroid disease is at play, this is not at all the complete answer (Hoefnagles, Biology 2nd Edition).
I believe the first step to recovering from or learning to live with a disease is to understand the biology of the disease itself. If you feed yourself the information, your mind and body both become more consciously informed of the processes at work in your body and how to adjust accordingly. This is why understanding the basic biology behind the functions of the thyroid is important to healing your body. Even though your body is a continuum, lets isolate part of the endocrine gland to increase our understanding of the thyroid.
“If you feed yourself the information, your mind and body both become more consciously informed of the processes at work in your body and how to adjust accordingly.”
Endocrine glands produce and secrete hormones into the bloodstream, hormones that travel through the bloodstream to alter your metabolism. The thyroid is one of these glands located in the neck. A chain of hormone-releasing actions results in the final hormone released by the thyroid that increases metabolism. The first in this chain is the hypothalamus, which releases a peptide hormone that targets the anterior pituitary. When this peptide hormone reaches the anterior pituitary, it stimulates the release of the thyroid-stimulating hormone (TSH) a glycoprotein that targets the actual thyroid gland. The thyroid gland secretes thyroxine and triiodothyronine. Two important effects of the release of these hormones are the increased absorption of nutrients by the small intestine and fat levels within cells and within the blood plasma to decline. When thyroid hormone levels are low, the hypothalamus amps up its release of thyrotropin-releasing hormone (TRH). This stimulates the anterior pituitary to release more TSH, thus stimulating the thyroid to release thyroid hormones (Hoefnagles, Biology 2nd Edition).
Individuals are commonly affected by hypothyroidism. “Hypo” meaning low or under; hypothyroidism means that the thyroid gland is not releasing enough hormones. The effect of hypothyroidism is generally a slow metabolic rate. Interestingly, hypothyroidism is usually treated with supplemental iodine. Iodine is important to the thyroid because thyroxin contains four atoms of Iodine and is therefor sometimes called T4 and triiodothyronine contains three atoms of Iodine; sometimes called T3. Iodine comes from the water vapor from the sea that forms rain. Rain is what carries Iodine to the soil for crops to use. Worldwide, low iodine levels remain the cause of most thyroid deficiency (Vanderpump, Thyroid Disease). Today, iodine is common in table salt; Americans rarely suffer from low levels of iodine (Hoefnagles, Biology 2nd Edition). In non-iodine deficient countries like the United States, hypothyroidism is caused by chronic autoimmune thyroiditis, also known as Hashimoto’s disease. The thyroid gland is one of the most common organs or tissues to be affected by autoimmune disease (Vanderpump, Thyroid Disease).
Thyroiditis can be obvious meaning the gland is painful or tender to the touch. Obvious thyroiditis can even cause discomfort when swallowing. “Silent thyroiditis” means that the thyroiditis does not cause any painful physical symptoms of the gland itself. Infection or inflammation of the gland is not at all uncommon and if the thyroiditis is obvious the inflamed thyroid could be under viral attack. Other signs that you might be suffering from hypothyroidism include slow heart rate, little bowel activity, dryness of the skin, intolerance of cold weather, depression, loss of hair, swelling around the eyes, and our favorite- weight gain.
“Other signs that you might be suffering from hypothyroidism include slow heart rate, little bowel activity, dryness of the skin, intolerance of cold weather, depression, loss of hair, swelling around the eyes, and our favorite- weight gain.”
Doctors test for a failing thyroid by testing the levels of TSH in the blood. This makes sense because when thyroid hormones are low, the pituitary gland responds by secreting more TSH. When TSH is high, your thyroid production is shy! Other tests for thyroid failure are those that test for free T4 in water of the blood. Something to know about T4 is that it is somewhat dependent on the amount of T4 that is already attached to transport proteins. Free T4 refers the “extra” T4 that does not have any transfer proteins left to attach to. Levels of T4 can be decreased when the number of carrier proteins is increased- causing hypothyroidism. Increase in carrier proteins (decrease in T4 in the blood) can be linked to anti-depressant drugs, Aspirin therapy, kidney disease, hereditary low, and more.
“When TSH is high, your thyroid production is shy!”
Antibodies can damage and destroy thyroid cells. Antibodies known as thyroid peroxidase (TPO) can be tested for and are usually found in the blood of people with Hashimoto’s thyroiditis. If you are suffering from “silent thyroiditis” it is most probable that your hypothyroidism is autoimmune associated. But it may not be a good idea to blame hypothyroidism immediately on these antibodies until you have investigated other options. From studies of thyroid overactivity we have seen that a significant number of people will develop hypothyroidism within 2-3 months of iodine therapy. Over-the-counter medicines, especially cough medicines, generally contain iodine. Prolonged use of these medications cause underactivity of the thyroid. Certain foods can also produce an anti-thyroid effect- these foods are cabbage, kale, and seaweed. Fortunately, as long as dietary iodine intake is sufficient the consumption of these vegetables does not induce hypothyroidism.
“Prolonged use of over-the-counter cough medications can cause underactivity of the thyroid.”
Besides the prior mentioned symptoms, women with hypothyroidism may notice their periods becoming heavier and last longer, short, stubby forearm hair, deepening of the voice, and a sensation of pins and needles in their fingers and hands especially during the night or upon waking. People with mild hypothyroidism can become depressed or anxious. Because depression is common, patients must be aware that depression even after correction of thyroid deficiency is common and is a cause for people to feel dissatisfied with their response to thyroid treatment. Thanks to modern medicine, great evidence supports the effectiveness of thyroid treatment and hypothyroidism should not go untreated! Many people around the world who have not yet found a better solution to treating hypothyroidism are using hormone replacement therapy. But is this the limit to treating hypothyroidism or are there better methods out there beyond the science of western medicine?
The number of people in the United States alone suffering from hypothyroidism who take some type of thyroid replacement hormone is an outstanding 10 million. Throughout the world as many as 200 million people are medicated with a thyroid replacement hormone for underactive thyroid. Thyroid problems are about 10 times more common in women than in men (Vanderpump, Thyroid Disease). Symptoms of an underactive thyroid can go unnoticed for years. If you think that you might be experiencing irregular symptoms at all you should consult with your doctor.
Information from this blog entry can be found in Thyroid Disease Fourth Edition by Mark P.J. Vanderpump and W. Michael G. Tunbridge