A goiter is an abnormal enlargement of the thyroid gland and can occur for a number of different reasons. The thyroid is a small, butterfly shaped gland inside the neck, just below your Adam's apple. The thyroid gland produces hormones which control the body's metabolism and regulate the rate at which the body carries out its functions.
The presence of an enlarged goiter usually means that the thyroid gland is not functioning normally. Causes of a goiter include an imbalance in the thyroid gland and Goiter symptoms generally occur in a gland that is overactive, producing too much hormone (hyperthyroidism), or that is underactive, producing too little hormone (hypothyroidism).
Goiter puts pressure on other parts of the neck such as the trachea and esophagus which makes it difficult to breathe and swallow. Often, goiters are also removed for cosmetic reasons. They are more common in women and the elderly.
Having a goiter doesn't necessarily mean that your thyroid gland isn't working normally. Even when it's enlarged, your thyroid may produce normal amounts of hormones. It might also, however, produce too much or too little thyroxine and T-3.
- Iodine deficiency. Iodine, which is essential for the production of thyroid hormones, is found primarily in seawater and in the soil in coastal areas. In the developing world, people who live inland or at high elevations are often iodine deficient and can develop goiter when the thyroid enlarges in an effort to obtain more iodine. The initial iodine deficiency may be made even worse by a diet high in hormone inhibiting foods, such as cabbage, broccoli and cauliflower. Although a lack of dietary iodine is the main cause of goiter in many parts of the world, this is not the case in First World countries, where iodine is routinely added to table salt and other foods.
- Graves' disease. Goiter can sometimes occur when your thyroid gland produces too much thyroid hormone (hyperthyroidism). In Graves' disease, antibodies produced by your immune system, which normally help protect against viruses and bacteria, mistakenly attack your thyroid gland, causing it to produce excess thyroxine. This overstimulation causes the thyroid to swell.
- Hashimoto's disease. Goiter can also result from an underactive thyroid (hypothyroidism). Like Graves' disease, Hashimoto's disease is an autoimmune disorder. But instead of causing your thyroid to produce too much hormone, Hashimoto's damages your thyroid so that it produces too little. Sensing a low hormone level, your pituitary gland produces more TSH to stimulate the thyroid, which then causes the gland to enlarge.
- Multinodular goiter. In this condition, several solid or fluid filled lumps called nodules develop in both sides of your thyroid, resulting in overall enlargement of the gland.
- Solitary thyroid nodules. In this case, a single nodule develops in one part of your thyroid gland. Most nodules are noncancerous (benign) and don't lead to cancer.
- Thyroid cancer. Thyroid cancer is far less common than benign thyroid nodules are. Cancer of the thyroid often appears as an enlargement on one side of the thyroid.
- Pregnancy. A hormone produced during pregnancy, human chorionic gonadotropin (HCG), may cause your thyroid gland to enlarge slightly.
- Inflammation. Thyroiditis is an inflammatory condition that can cause pain and swelling in the thyroid.
Goitrogens are naturally-occurring substances that can interfere with function of the thyroid gland. Goitrogens get their name from the term "goiter," which means an enlargement of the thyroid gland. If the thyroid gland is having difficulty making thyroid hormone, it may enlarge as a way of trying to compensate for this inadequate hormone production. "Goitrogens," like circumstances that cause goiter, cause difficulty for the thyroid in making its hormone.
There are two general categories of foods that have been associated with disrupted thyroid hormone production in humans: soybean-related foods and cruciferous vegetables. In addition, there are a few other foods not included in these categories - such as peaches, strawberries and millet - that also contain goitrogens. The table below shows a list of some foods that contain goitrogens.
Included in the category of soybean related foods are soybeans themselves as well as soy extracts, and foods made from soy, including tofu and tempeh. While soy foods share many common ingredients, it is the isoflavones in soy that have been associated with decreased thyroid hormone output. Isoflavones are naturally-occurring substances that belong to the flavonoid family of nutrients. Flavonoids, found in virtually all plants, are pigments that give plants their amazing array of colors. Most research studies in the health sciences have focused on the beneficial properties of flavonoids, and these naturally occurring phytonutrients have repeatedly been shown to be highly health supportive.
The link between isoflavones and decreased thyroid function is, in fact, one of the few areas in which flavonoid intake has called into question as problematic. Isoflavones like genistein appear to reduce thyroid hormone output by blocking activity of an enzyme called thyroid peroxidase. This enzyme is responsible for adding iodine onto the thyroid hormones. (Thyroid hormones must typically have three or four iodine atoms added on to their structure in order to function properly.)
A second category of foods associated with disrupted thyroid hormone production is the cruciferous food family. Foods belonging to this family are called "crucifers," and include broccoli, cauliflower, Brussels sprouts, cabbage, mustard, rutabagas, kohlrabi, and turnips. Isothiocyanates are the category of substances in crucifers that have been associated with decreased thyroid function. Like the isoflavones, isothiocyanates appear to reduce thyroid function by blocking thyroid peroxidase, and also by disrupting messages that are sent across the membranes of thyroid cells.
In the absence of thyroid problems, there is no research evidence to suggest that goitrogenic foods will negatively impact your health. In fact, the opposite is true: Fermented soy products and cruciferous vegetables have unique nutritional value, and intake of these foods has been associated with decreased risk of disease in many research studies. That's one of the reasons we've included both types of food among the World's Healthiest Foods!
Because carefully controlled research studies have yet to take place on the relationship between goitrogenic foods and thyroid hormone deficiency, healthcare practitioners differ greatly on their perspectives as to whether a person who has thyroid problems, and notably a thyroid hormone deficiency, should limit their intake of goitrogenic foods. Most practitioners use words like "overconsumption" or "excessive" to describe the kind of goitrogen intake that would be a problem for individuals with thyroid hormone deficiency. Here the goal is not to eliminate goitrogenic foods from the meal plan, but to limit intake so that it falls into a reasonable range.
Limiting goitrogenic intake is often much more problematic with soy foods than with cruciferous vegetables, since soy appears in so many combination and packaged food products in hidden form. Ingredients like textured vegetable protein (TVP) and isolated soy concentrate may appear in foods that would rarely be expected to contain soy. A standard, one cup serving of cruciferous vegetables 2 to 3 times per week, is likely to be tolerated by many individuals with thyroid hormone deficiency. It's worth it to try and include these foods in a meal plan because of their strong nutritional value and great track record in preventing many kinds of health problems.
Although research studies are limited in this area, cooking does appear to help inactivate the goitrogenic compounds found in food. Both isoflavones (found in soy foods) and isothiocyanates (found in cruciferous vegetables) appear to be heat sensitive, and cooking appears to lower the availability of these substances. In the case of isothiocyanates in cruciferous vegetables like broccoli, as much as one third of this goitrogenic substance may be deactivated when broccoli is boiled in water.
Although for many people goitrogens do not seem to pose a health concern, certain individuals who have thyroid problems may be advised by their healthcare practitioner to limit excessive consumption of foods that contain these compounds. As cooking seems to help to inactivate the goitrogenic compounds found in food, it seems reasonable to conclude that for individuals with deficient thyroid hormone production, steaming of cruciferous vegetables like broccoli makes good sense, as does consumption of tofu in cooked versus raw form.
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