As many as 20 million Americans are suffering from some form of thyroid problem and of these, low thyroid function is probably the most prevalent, especially in women. The function of the thyroid gland is to take in iodine, which is found in many foods and convert it into thyroid hormones T4 [thyroxine] and T3 [triiodothyronine]. T4 is produced by the thyroid gland in much greater amounts than T3 about 90% more, but T3 is the biologically active hormone that influences every cell in the body. An enzyme is required to convert T4 to T3 and this enzyme needs both zinc and selenium to do so. However taking thyroid medication e.g. Synthroid can further deplete both zinc and selenium, as it calls for increased activity of the converting enzyme.
The transport of thyroid hormone is extremely important and must be clearly understood to effect a workable solution to hyperthyroidism. The normally prescribed treatments and tests today are based on a “free hormone” hypothesis formulated in 1960 which assumes that the concentration of free hormones T4 and T3 in blood serum determines the rate at which and how much is taken up by the cells demonstrating how much T3 is in the cells. Unfortunately this is not true, shown by many recent studies e.g. by Hennemann G, Doctor R, Freisema EC, De Jong M et al. Plasma membrane transport of thyroid hormones and its role in thyroid hormone metabolism and bioavailability. Endocrine Reviews 2001;22(4);451-476.
Hormones secreted by the thyroid interact with all other hormones in the body e.g. insulin, cortisol, estrogen, progesterone, and testosterone. The transport of thyroid hormones are energy dependent, so any condition that is connected with low production of cellular energy will affect this transport into the cells, creating hypothyroidism in the cells in spite of appearing normal in the standard blood tests. Conditions affecting cell energy production include; insulin resistance, diabetes and obesity, chronic and acute dieting, depression, anxiety, bipolar depression, neurodegenerative diseases, aging, chronic fatigue syndrome, fibromyalgia, migraines, chronic infections, stress and anxiety, cardiovascular disease, inflammation and chronic illness, and those with high triglycerides and high cholesterol. From this we can see that standard blood tests can be very unreliable if these common conditions are present.
Deiodinase is the enzyme group that converts T4 to T3 and there are three of these D1, D2, and D3, which occur mostly on the liver, kidney and thyroid gland. D1 converts T4 to T3 in the body and peripheral cellular tissue, BUT D2 converts T4 to T3 only in the pituitary and is a thousand times more effective at the conversion but ONLY in the pituitary. The pituitary is different to every other cell in the body. It is in this gland that the Thyroid Stimulating Hormone known as THS is produced. The levels of THS are controlled by how much T3 is in the pituitary and this does NOT equate to the levels of T3 in the body tissues. Hence using THS levels as a test for the body thyroid levels is totally inaccurate.
D2 is much less affected by toxins and medications than D1 which converts T4 to T3 in the rest of the body. D1 activity is reduced by many factors such as emotional and physiological stress, depression, dieting, weight gain, PMS, diabetes, leptin resistance, fibromyalgia, inflammation, autoimmune disease, and chronic illness. In contrast D2 reacts to all these factors by increasing pituitary T4 to T3 conversion and so keeps the TSH levels normal while the body tissues are crying out for T3 which is not happening in the body. This was investigated by doctors at Harvard Medical School and these findings were published in a review in the Endocrine Reviews. Many other published reviews reported similar findings.
D3 converts T4 to reverse T3 and is not present in the pituitary gland. Reverse T3 is a competitive inhibitor of T3 and blocks T3 from binding to its receptors and so blocking the T3 effects by reducing metabolism. Reverse T3 stops D1 converting T4 to T3 in the body and blocks their uptake by the cells, and so reduces T3 levels and hence thyroid activity. Reverse T3 is seen with various concentrations in different tissues. More is produced during chronic physical stress and illness and indicates reduced T4 to T3 conversion and so low intracellular T3 levels even though TSH levels are normal because the pituitary is not affected by it and it is the pituitary that controls TSH levels.
Stress reduces D1 and increases D3 activity and so decreases thyroid activity; BUT it stimulates D2 activity in the pituitary causing more conversion to T3 in the pituitary and so keeping THS levels normal when the body needs T3. Inflammation reduces D1 activity and stops T4 to T3 conversion in tissues and inflammatory cytokines increase D2 and so make the pituitary produce T3 and so reducing TSH levels despite the body desperately needing T3. Toxins also depress D1 but do not affect D2. Bisphenol-A found in large amounts in the environment can leach into foods and liquids from plastic bottles and block thyroid activity in all tissues except the pituitary causing weight gain, fatigue and depression.
It is clear that to be thoroughly evaluated for thyroid dys- function THS and T4 levels do not give the correct information. Reverse T3 to T3 ratio levels need to be considered. This is particularly necessary where physical and emotional stress, depression, dieting, obesity, leptin and insulin resistance, diabetes, chronic fatigue, fibromyalgia, inflammation, auto- immune disease and chronic illness are concerned. As you can see the whole endocrine system is extremely complicated and the chemical reactions are too numerous to explain and difficult to understand. Trying to sort out what is affecting ones thyroid is like searching for the proverbial needle in a haystack. I believe that stress is one of today’s main factors. Stress disrupts the adrenals which in turn has an extensive effect on the thyroid. Many other biological and environmental problems also play their part in disrupting thyroid function. Gut health and the foods we consume are pivotal to overall health and changing ones diet can go a long way to balancing the function of major body systems.
Natural remedies can play their part too. Ashwaganda is an adaptogen herb that helps the body respond to stress and helps lower cortisol and so balance T4 levels. Other adaptogens such as Rhodiola Licorice root, ginseng, holy basil have similar benefits. Selenium is needed for the production of T3 and improves thyroid structure. Fish oil which contains fatty acids help with thyroid symptoms including anxiety, depression, inflammatory bowel disease, arthritis and diabetes. This list could go on and on, so it is better for one to talk to a health professional who has researched beyond what the historical consensus statement of treatment today.
I have found the information presented on the nahyprothyroidism.org site invaluable in my search for the real reasons for hypothyroidism and my continuing search for effective remedial treatments.
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