“We summarized that adequate iodine nutrition of 150 mcg a day is essential for normal thyroid function but that an excessive intake—be it from a variety of sources (eg, fortified salt, supplements, seaweed, seafood)—can have the reverse effect: too much iodine can cause hypothyroidism and hyperthyroidism and too little iodine low may lead to hypothyroidism,” Dr. Leung says.
Hyperthyroidism, particularly Graves’ disease, is known to cause bone loss, which is compounded by the vitamin D deficiency commonly found in people with hyperthyroidism. This bone mass can be regained with treatment for hyperthyroidism, and experts suggest that adequate bone-building nutrients, such as vitamin D, are particularly important during and after treatment.13
• Vitamin B12: Studies have shown that about 30% of people with ATD experience a vitamin B12 deficiency. Food sources of B12 include mollusks, sardines, salmon, organ meats such as liver, muscle meat, and dairy. Vegan sources include fortified cereals and nutritional yeast. Severe B12 deficiency can be irreversible, so it’s important for dietitians to suggest clients with thyroid disease have their levels tested.16
An amino acid used in the synthesis of thyroid hormones. Thyroxin (T4) is naturally produced from the iodination of tyrosine, a nonessential amino acid obtained both from protein-containing dietary sources and through the body making some itself. Supplementing with L-tyrosine has been shown to improve sleep deprivation and can help combat fatigue and a poor mood by improving alertness and neurotransmitter function. One reason L-tyrosine is beneficial in healing thyroid symptoms is because it plays a role in the production of melatonin, dopamine and/or norepinephrine, which are our natural “feel good” hormones. L-tyrosine is available by the brand Pure Encapsulations.
The thyroid is the organ with the highest selenium content in the whole body. Selenium is necessary for the production of the T3 thyroid hormone and can reduce autoimmune affects. In patients with Hashimoto’s disease and in pregnant women with thyroid disturbances, selenium supplementation decreases anti-thyroid antibody levels and improves the structure of the thyroid gland.
Because it helps balance hormone levels, selenium can lower the risk for experiencing thyroid disorder during pregnancy (postpartum thyroiditis) and afterward. (15) Other studies have shown that when selenium deficiency is resolved through supplementation, patients experience on average 40 percent reduction in thyroid antibodies compared to a 10 percent increase when given a placebo. (16)
These clinical trials also began to define the adverse-effect profiles associated with these agents; thyrotoxicosis was frequently encountered. Patients treated with l-triiodothyronine3 (100 to 175 mcg/d) normalized BMR faster than did those receiving desiccated thyroid (120 to 210 mg/d) or l-thyroxine (200 to 350 mcg/d) but were more likely to experience angina (32). Desiccated thyroid was also associated with adverse symptoms in other studies; muscle stiffness, psychosis, and angina all occurred (33). In a crossover study of l-triiodothyronine monotherapy (75 to 100 mcg/d), l-thyroxine monotherapy (200 to 300 mcg/d), and desiccated thyroid (1.5 to 3 grains/d), all of these therapies restored BMR and serum PBI; with l-triiodothyronine, however, angina and heart failure occurred. Dose reduction corrected these adverse effects, but authors concluded that l-thyroxine monotherapy or thyroid extract was preferred (34). In a trial of l-thyroxine monotherapy at doses of 200 to 300 mcg/d versus l-thyroxine (80 mcg) plus l-triiodothyronine (20 mcg) daily, patients receiving the combination had such symptoms as palpitations, nervousness, tremor, and perspiration (35). Some early proponents of l-thyroxine monotherapy emerged because of less frequent thyrotoxic effects (24), but it is difficult to determine whether such adverse effects were related to the agent used or its high dosage. Thyrotoxic adverse effects were typically remediable by simple dose reduction (36), so desiccated thyroid remained the preparation of choice (37).
Medications that are used to treat an overactive thyroid (hyperthyroidism) may cause hypothyroidism. These drugs include methimazole (Tapazole) and propylthiouracil (PTU). The psychiatric medication, lithium (Eskalith, Lithobid), is also known to alter thyroid function and cause hypothyroidism. Interestingly, drugs containing a large amount of iodine such as amiodarone (Cordarone), potassium iodide (SSKI, Pima), and Lugol's solution can cause changes in thyroid function, which may result in low blood levels of thyroid hormone.
If you're thinking about upping your intake of salty, processed foods just to fit more iodine into your diet, think again. More than 75% of our dietary sodium intake comes from restaurant, pre-packaged, and processed fare. (In fact, you'd probably be surprised to learn just how many foods are actually just hidden salt traps.) But "manufacturers don't have to use iodized salt in their products," says Ilic. And according to the National Institutes of Health's Office of Dietary Supplements, they "almost never" do. The upshot: You may be taking in too much sodium (which can set you up for high blood pressure, then heart disease), minus the iodine.
Thyroid hormones regulate cholesterol synthesis, cholesterol receptors, and the rate of cholesterol degradation. Hypothyroidism increases LDL levels, and increased cholesterol levels have been shown to induce hypothyroidism in animal models. Normalization of thyroid hormone levels has a beneficial effect on cholesterol, which may be worth noting especially for clients who choose not to take prescribed thyroid medications.7
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Cruciferous vegetables, such as broccoli and cabbage, are full of fiber and other nutrients, but they may interfere with the production of thyroid hormone if you have an iodine deficiency. So if you do, it’s a good idea to limit your intake of Brussels sprouts, cabbage, cauliflower, kale, turnips, and bok choy, because research suggests digesting these vegetables may block the thyroid's ability to utilize iodine, which is essential for normal thyroid function.
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