The Thyroid

by Katalin Ferencz-Biro, PhD

What is the thyroid?

Anatomical position: The thyroid is a 2-inch-long, butterfly-shaped gland weighing less than 1 ounce. It is located in the front of the neck below the larynx. It has two lobes, one on either side of the windpipe.

Function of the thyroid:

The thyroid is one of the glands that make up the endocrine system. The glands of the endocrine system produce and store hormones and release them into the bloodstream. The hormones then travel through the body and direct the activity of the body’s cells. The produced hormones control major functions including weight management, how we use energy, how we metabolize food, and even how we sleep.

What are the thyroid hormones?

The thyroid gland is regulated by the pituitary gland. The pituitary gland is positioned in the brain. The pituitary gland releases the thyroid stimulating hormone (TSH). The TSH stimulates the thyroid gland to release thyroid hormones. After several different molecular conformational and structural changes the final hormones are the Thyroxine (T4) and Triiodothyronine (T3). Number 3 and 4 refer the iodine molecules present in different forms of thyroid hormones. Therefore iodine is essential for the correct function of thyroid. Iodine deficiency could lead to goiter, autoimmune thyroid problems, even increased risk of thyroid cancer.

Physiologic effects of thyroid hormones

It is likely that all cells in the body are targets for thyroid hormones.

Thyroid hormones have an effect on physiologic processes, such as metabolism, growth and development.

Metabolism:

Excess thyroid hormones lead to an increase in basal metabolic rate.

Lipid metabolism: Increased thyroid hormone levels stimulate fat mobilization, leading to increased concentrations of fatty acids in plasma. They also enhance oxidation of fatty acids in many tissues. The plasma concentrations of cholesterol and triglycerides are inversely correlated with thyroid hormone levels - one diagnostic indication of hypothyroidism is increased blood cholesterol concentration.

Carbohydrate metabolism: Thyroid hormones stimulate carbohydrate metabolism, including enhancement of insulin-dependent entry of glucose into cells and increased gluconeogenesis and glycogenolysis to generate free glucose.

Growth:

Thyroid hormones are clearly necessary for normal growth in children. In case of thyroid hormone deficiency, growth-retardation could be observed.

Development: 

Normal levels of thyroid hormone are essential to the development of the fetal and neonatal brain.

Other Effects:

Thyroid hormones are affecting all organs and tissues in our body. Thyroid hormones are the “conductor” of our endocrine system.

  • Cardiovascular system: Thyroid hormones increase heart rate, cardiac contractility and cardiac output. They also promote vasodilation, which leads to enhanced blood flow to many organs.
  • Central nervous system: Both decreased and increased concentrations of thyroid hormones lead to alterations in mental state. Too little thyroid hormone, and the individual tends to feel mentally sluggish, while too much induces anxiety and nervousness.
  • Reproductive system: Normal reproductive behavior and physiology is dependent on having essentially normal levels of thyroid hormone. Hypothyroidism in particular is commonly associated with infertility.

Thyroid function disorders

Hyperthyroidism is a disorder caused by too much thyroid hormone in the bloodstream, which results overactive metabolic state. Could lead to the following symptoms:

Weight loss, nervousness, anxiety, irritability, increased perspiration, racing heart, hand tremors, difficulty sleeping, increased bowel movements, fine, brittle hair, muscle weakness etc.

Most often, hyperthyroidism is caused by an autoimmune disorder called Graves’ disease. In this case the immune system produces antibodies that stimulate the thyroid, causing it to produce too much T4 hormone.

Hypothyroidism is a disorder that occurs when the thyroid doesn’t make enough thyroid hormone for the body’s needs. Without enough thyroid hormone, many of the body’s functions slow down. The symptoms of low thyroid disorder:

Brittle nail, cold intolerance, constipation, depression, dry skin and hair, fatigue, hair loss, inability to concentrate, infertility, irritability, muscle weakness and cramps, nervousness, weight gain, etc.

Autoimmune disease: the thyroid gland attacked by the body’s antibodies, (Hashimoto’s disease), what causes inflammation and swelling of thyroid gland (goiter).

It is possible that the body manifests different kinds of thyroid disorders at the same time for example: hypo- and hyperthyroidism.

How to check thyroid function:

Tests:

  • Blood tests: for TSH, T4, T3, thyroid-stimulating immunoglobulin (TSI), antithyroid antibody test, also called the thyroid peroxidase antibody test (TPOab), iodine concetration
  • Imaging tests: ultrasound of the thyroid, thyroid scan, radioactive iodine uptake test
  • Function tests: to access how well the tyroid is working
  • Biopsy of nodule in the neck to decide of nodule is benign or cancerous

Possible underlying causes of thyroid disorders (the list below is not all inclusive)

Infections

Toxic chemicals

From environment (mercury, pesticides, herbicides, etc.),

From food, (for example: preservatives, additives for processed foods, toxic substances which displace iodine, such as fluoride, bromide)

Food allergies

Gluten intolerance

Iodine deficiency, a major issue

Severe emotional stress

Family history

Thyroid function support by nutrition and stress management

Nutrition:

Iodine: kelp, seaweed, iodine enriched salt

The daily iodine requirement is 150 microgram (ug). Consuming too much iodine is not beneficial.

Iodine, is essentially needed to make the necessary thyroid hormones to support all of the tissues in the body. Thyroxine (T4) and Triiodothyronine (T3) are the most essential, active, iodine-containing hormones.

Trace metals: Selenium, Zinc, Iron and Copper

Foods can help provide trace minerals are: calf’s liver, organ meat, poultry, red meat, oysters, spinach, mushrooms, turnip greens and Swiss chard, garlic, onions, olive oil, pumpkin seeds

Foods are rich in copper: organ meats, oysters, clams, crabs, cashews, sunflower seeds, wheat bran cereals, whole-grain products, and cocoa products.

Foods are high in iron: leafy green vegetables, beans, shellfish, red meat, and poultry.

The iron intake should be complemented with adequate amounts of vitamin C from foods such as citrus fruits, red berries, tomatoes, potatoes, and bell peppers in order to help maximize the body’s iron absorption efficiency.

Omega-3 Fats:

These essential fats, which are found in fish or fish oil. It  plays an important role in thyroid function, by making cells become sensitive to thyroid hormone.

Coconut Oil:

Coconut oil is made up of mostly medium-chain fatty acids, which may help to increase metabolism and promote weight loss.

Antioxidants and B Vitamins:

The antioxidant vitamins A, C and E can help your body neutralize oxidative stress that may damage the thyroid. In addition, B vitamins help to manufacture thyroid hormones and play an important role in healthy thyroid function.

Stress management by different relaxation techniques.

Foods to avoid for thyroid health

There are certain foods that negatively affect thyroid function.

Goitrogens are naturally occurring chemicals in plants which can disrupt normal thyroid function when they are in raw, uncooked form.

Sulfur containing vegetables:

(This chemical is crossing the placenta, and could affect the thyroid function development of fetus.)

Sulfur containing vegetables are: bamboo shoots, cassava (tapioca made from it), corn, flax, lima beans, sweet potato.

Thiocyanites containing vegetables:   

Cruciferous vegetables: after cutting the vegetable thiocyanites are forming in the plant.

They are: arugula, canola, cauliflower, broccoli, cabbage, collard greens, horseradish, kale, kohlrabi, mustard greens, mustard seeds, radishes, rutabagas, turnips, wasabi, watercress

COOKING, SOAKING, STEAMING and FERMENTATION REDUCE the thiocyanate level. Limit intake 5 oz/day, if possible avoid uncooked vegetables from this group.

While it’s true that large amounts could interfere with thyroid function, especially if eaten raw, these veggies offer a myriad of other health benefits that make the benefits outweigh the risks for most but not all people.

Soy isoflavones:

Foods: Soy milk, tofu, soy, soybean oil, soy burgers, processed soy foods, may lead to decreased thyroid function.

COOKING DOES NOT DESTROY the negative effects of soy products on thyroid function.

Fermented soy products, including miso, natto, tempeh and traditionally brewed soy sauce, are safe to eat, as the fermentation process reduces the goitrogenic activity of the isoflavones.

Millet flavonoids (Apigenin):

Foods: millet, chamomile, citrus fruit, parsley, onions, wheat sprouts, red wine, beer

COOKING DOES NOT DESTROY the negative effects of millet flavonoids on thyroid function.

Aspartame:

There is concern that the artificial sweetener aspartame, sold under the brand name Nutrasweet, may trigger Graves’ disease and other autoimmune disorders in some people. The chemical may trigger an immune reaction that causes thyroid inflammation and thyroid autoantibody production.

Gluten:

Gluten is a potential goitrogen and can also trigger autoimmune responses (including Hashimoto’s thyroiditis) in people who are sensitive. Gluten is found in wheat, rye and barley, along with most processed foods.

Simple carbohydrates:

Foods: white sugar, dried fruits, honey, maple, white bread, white pasta

References:

David Brownstein, Iodine: why you need it, why you can’t live without it, Medical Alternatives Press, 4th Edition, 2009
 
R. Bowen: Mechanism of Action and Physiologic Effects of Thyroid Hormones, http://arbl.cvmbs.colostate.edu/hbooks/pathphys/endocrine/thyroid/index.html