What Is the Thyroid?
Tucked away just below your Adam’s apple, the thyroid gland doesn’t look like much, but it’s one of the most important parts of endocrine system, the network of glands that regulate your hormones. The thyroid is a particularly important part of the endocrine network because it controls how sensitive your body is to other hormones. And endocrine cells aren’t the only ones affected by thyroid function: every cell in the body has receptors for thyroid hormone, making it crucial to proper metabolism, growth, and cardiovascular and reproductive health.
When the endocrine system is working properly, the hypothalamus produces a hormone called TRH, which stimulates the anterior pituitary gland to produce Thyroid Stimulating Hormone (TSH). TSH, in turn, prompts the thyroid to produce its own hormones. The thyroid is responsible for the hormone calcitonin (which causes your bones to absorb calcium), T3, and T4. The latter two are by far the most important, and they’re really both forms of the same hormone: T3 is the active form, while T4 must be converted into T3 by other organs (the liver, gut, muscles, and thyroid) before it can perform its proper role in the body. Since the thyroid produces much more T4 than T3, this conversion process is essential to keeping your hormone levels at the proper balance. To keep your hormone levels stable, a sufficient amount of T4 signals the anterior pituitary to stop producing TSH, pausing the production of T4 until you need more.
This is the ideal situation. But the thyroid hormones can become disrupted by one or more of several factors, causing either hypothyroidism (not enough of thyroid hormone), hyperthyroidism (too much of them), or both at once. Since the thyroid is so important in regulating metabolism, these conditions can have very serious side effects. Patients suffering from hypothyroidism feel constantly cold, tired, and run-down. They often gain weight for no apparent cause. Hypothyroidism can also raise your serum cholesterol levels (since T3 allows your cells to use cholesterol for energy, while low levels of T3 will keep the cholesterol circulating in your blood). In contrast, hyperthyroidism presents some of the opposite symptoms. Patients with hyperthyroidism also commonly feel tired, but they often feel too hot and suffer from unexplained weight loss.
Thyroid problems are dangerous – and they can often go undiagnosed for quite some time, since the symptoms are so vague and general, and most people barely even know what the thyroid is. To make it worse, the modern diet and environment consistently exposes us to all kinds of stressors and toxins that can further damage an already sick thyroid gland. Fortunately, by understanding how and why thyroid problems develop, most people can avoid them in the first place, or at least effectively treat the symptoms if they do occur.
Thyroid Dysregulation and Autoimmunity
Hyper- and hypothyroidism are often really two sides of the same coin, and the same underlying disease can sometimes cause both sets of symptoms. Therefore, it makes more sense to think of thyroid symptoms as a large group of related problems primarily attributable to autoimmune reactions and metabolic dysregulation.
Two specific autoimmune disorders are linked to thyroid symptoms: Hashinoto’s Disease (or Hashimoto’s Thyroiditis) and Graves’ Disease. An autoimmune disease is a disease that causes your immune system to attack your own body as though it were a foreign invader; these two specific autoimmune conditions target the thyroid. In other words, they trick your body into thinking that your own thyroid is a dangerous enemy that needs to be attacked and destroyed.
Hashimoto's Disease (or Hashimoto’s Thyroiditis) can cause an initial case of hyperthyroidism when it destroys the cells of the thyroid, causing them to release a surge of thyroid hormone into the bloodstream. As the disease progresses, however, it damages the thyroid so severely that it can no longer even produce a normal amount of thyroid hormone. Thus, while symptoms of Hashimoto’s begin as hyperthyroidism, the later stages of the disease can often cause both sets of symptoms. A transient form of Hashimoto’s called postpartum thyroiditis is a condition that causes a woman to develop thyroiditis after giving birth – as with other forms of Hashimoto’s, this can result in hyper- or hypothyroidism, or both. Graves’ disease, another autoimmune disorder, accounts for most cases of hyperthyroidism. In patients with Graves’ disease, the immune system’s attacks on the thyroid overstimulate it, causing it to produce too much T3 and T4. Unlike Hashimoto’s, Graves’ disease does not attack the thyroid itself, so hyperthyroid symptoms are never replaced by hypothyroidism.
Compounding the problem, autoimmune conditions like Grave’s and Hashimoto’s cause inflammation, which makes cells less receptive to thyroid hormone. Inflammation also causes the body to stop converting T4 to T3. Thus, even though the thyroid might be producing enough T4, it’s not being converted into a form your body can use, so it doesn’t do you any good.
The causes of these autoimmune disorders are still under investigation - genetics probably play a part, but cannot explain the whole story. Most probably, genetics and environment are both important. Some infections seem to increase the risk of thyroid autoimmunity; stress also plays a role. Of course, diet is also very important in the development of autoimmune diseases, as discussed later in the article.
Thyroid Dysregulation and Metabolism
The thyroid plays an important role in regulating metabolism, and thyroid disorders often present with metabolic symptoms like weight loss or gain, and a change in resting body temperature. But the link between the thyroid and the metabolism isn’t a one-way street: since the thyroid needs healthy levels of insulin to function correctly, proper metabolic regulation is also essential to thyroid health, and metabolic problems can set off a chain of thyroid symptoms, or make an existing problem even worse.
These metabolic problems, like so many other diseases, result from extremes. A diet too high in carbohydrates (especially simple carbohydrates) combined with a sedentary lifestyle, causes insulin resistance, metabolic syndrome, and diabetes. These diseases are strongly correlated with thyroid disorders (people who have one are much more likely to have the other as well - Type 1 Diabetes, which is also an autoimmune disorder, is especially strongly related to thyroid disorders). This is a logical and unsurprising connection: since insulin surges damage the thyroid, the insulin resistance caused by metabolic syndrome and diabetes puts it under extreme stress, preventing it from producing hormones properly. Both hyperthyroidism and hypothyroidism can also contribute to further insulin resistance, sparking a vicious circle of more metabolic and thyroid problems.
Thus, metabolic dysregulation caused by insulin resistance can produce thyroid symptoms and contribute to other causes of thyroid disorders. However, it’s also important to note that a diet completely lacking in carbohydrates, especially for an active person, can also cause problems. Although an excess of carbohydrates is by far more common in modern society, the dangers of a zero carbohydrate diet make it important for anyone – but especially people with thyroid problems – to avoid going to the other extreme to compensate.
This unfortunate side effect of a very low carbohydrate intake is especially intriguing to anyone following a Paleo diet, since Paleo meals tend to be much lower in carbohydrates than the standard American diet. Essentially, if you eat a diet low in glucose, your body thinks that you’re experiencing food scarcity (famine). Responding to the threat of starvation, it slows your metabolism and does everything possible to conserve precious glucose for your brain: reproductive function and athletic performance are nice, but if your brain isn’t getting the nourishment it needs, they won’t do you any good.
Since the thyroid is responsible for the rate of your metabolism, it is obviously a very important part of this response. But the hormonal changes involved also affect thyroid function because the liver needs glucose to convert T4 to T3. When all available glucose is being conserved for your brain, this process must be temporarily put on hold. Moreover, one of the essential functions of T3 is to transport glucose into other cells: this also has to stop to save glucose. Thus, in a period of glucose deficiency, T4 is instead converted into the inactive form reverse T3 (rT3), which does not transport glucose into cells.
Thus, a low carbohydrate diet (or a starvation diet of any kind, including an eating disorder) can cause something called Non-Thyroidal Illness Syndrome or Euthyroid Sick Syndrome (a name that literally means “healthy thyroid sick syndrome”), a problem where your thyroid gland is functioning normally, but your thyroid hormones are not produced in the proper proportions. This causes all the symptoms of hypothyroidism even with a healthy thyroid – clearly an outcome most of us want to avoid.
As with any recommendation that dietary carbohydrates might actually be healthy, this suggestion has sparked a healthy amount of debate within the Paleo community. Advocates of a very low carbohydrate diet disagree that carbs are helpful for thyroid health. Claiming that a lower metabolic rate promotes longevity, they argue that the slight metabolic downregulation brought on by a low-carbohydrate diet is not actually a problem. In some ways, this line of argument parallels one of the contestations against safe starches – that dietary glucose might be optimal for reproductive health and species survival, but that it doesn’t promote health beyond the age of child-raising.
In the end, dietary carbohydrates and metabolic function clearly have an effect on thyroid function, but the optimal carbohydrate consumption is different for every person, with a large range of possible healthy intake of starch – or even sugar – that depends on many different factors.
Thyroid Symptoms: Other Causes
As Euthyroid Sick Syndrome shows, hypothyroid symptoms don’t necessarily indicate a problem with the thyroid itself. Dietary stress (inadequate dietary carbohydrates or a starvation diet) can trigger this kind of problem, but other kinds of stress – like severe illness – can also provoke it. The inflammation associated with these stressors probably plays a primary role in causing hormonal dysfunction even in a patient with a healthy thyroid gland. Thyroid hormone resistance is another such problem: although this is very rare, it can cause your tissues to be resistant to thyroid hormone, causing elevated levels of T3 and T4 and symptoms of goiter (inflammation of the thyroid).
Furthermore, problems related to the thyroid can also result from the thyroid getting the wrong messages from other parts of the endocrine system. For example, if the pituitary gland is not working correctly (due to stress or other causes), it can send the wrong signals to the thyroid, resulting in hypothyroid symptoms even though the thyroid itself is functioning fine.
More rarely, problems with the thyroid can spring from causes that aren’t fully explained by either metabolism or autoimmunity. Hypothyroidism can also be a kind of birth defect, found in babies whose mothers were severely iodine deficient during pregnancy; for some people, genetic causes probably also play a role. Needless to say, diet is also a very important factor to consider – especially since the thyroid is so intimately connected with metabolism.
Micronutrients and Thyroid Function
As discussed above, macronutrients (especially carbohydrates) have a serious effect on the thyroid, but it’s important not to get caught up in the “big three” and lose sight of the micronutrients involved. One nutrient particularly important for proper thyroid function is iodine. The relationship between iodine and thyroid health is very complicated, however: iodine deficiency can provoke hypothyroid symptoms, but for people with existing thyroid problems, consuming more iodine can actually make the problem worse!
Iodine deficiency is the most common contributing factor to thyroid problems worldwide, but it’s rare in the Western world because all of our salt is fortified with iodine. Although iodine consumption is generally adequate, however, a class of naturally occurring pesticides called goitrogens can prevent the thyroid from absorbing enough iodine, causing the symptoms of deficiency even on an iodine-sufficient diet. Thyroid problems are thus closely related to an overload of goitrogenic foods, which include cruciferous vegetables like broccoli, cauliflower, and kale. This doesn’t mean that these foods are necessarily unhealthy; it does mean that when you eat them, you should increase your iodine intake to match.
Since iodine can both prevent and exacerbate thyroid problems, determining how much of it you should eat can be a challenge. Some doctors recommend iodine as a cure-all for thyroid symptoms; others are more cautious. If you already have thyroid problems – especially autoimmune problems – talk to your doctor before you start any kind of iodine supplement regimen. On the other hand, if you’re healthy and just want to prevent problems from occurring, it is important to make sure you get enough dietary iodine. Try some seasoned seaweed as a snack, eat seafood regularly, or just prepare your meals with iodized salt. If you have serious thyroid problems, you might also want to consider boiling cruciferous vegetables, since boiling breaks down 90% of the problematic chemicals, making them much easier on your system.
The question of iodine supplementation is inextricably tied up with another micronutrient: selenium. As well as offsetting any potential drawbacks of excess iodine supplementation, selenium also shows promise as an anti-inflammatory treatment for autoimmune thyroid conditions. Furthermore, your body needs selenium to convert T4 to T3, so selenium deficiency can cause hypothyroid symptoms even if the thyroid is functioning well. On the other hand, it’s also important not to overdose on selenium, as this can also worsen thyroid symptoms. In short, the balance of iodine and selenium is the important goal. An overdose of one is doubly harmful with a deficiency of the other: if you supplement iodine, it’s a good idea to supplement selenium proportionally. For everyone, it’s probably best to start out by making an effort to eat foods rich in these micronutrients, and use supplement pills as a last resort.
Vitamin D is another very important factor in preventing and treating thyroid disorders: deficiency is associated not only with autoimmune disorders in general and thyroid autoimmunity in particular, but also with insulin resistance and blood sugar dysregulation. Even in someone who spends enough time outside, many of the other causes of thyroid symptoms – leaky gut, stress, metabolic syndrome, and inflammation – reduce the ability of the body to use Vitamin D. Thus, someone with thyroid symptoms might need to get even more Vitamin D than a healthy person to get the same effect. As with any supplement, however, it’s very unwise to rush out to the drugstore and down the whole bottle: too much Vitamin D puts you at risk for toxicity, especially if you’re not getting enough of Vitamins A and K. If you can’t get your Vitamin D by spending time outside in the sun, begin with a lower dose of supplements and work your way up.
In conclusion, although several different micronutrients are important for healthy thyroid function, humans weren’t designed to eat any one vitamin in isolation – our bodies are complex systems, and the levels of one vitamin can affect all the others, causing potentially dangerous consequences if we start supplementing without regard for the bigger picture. If you have any disease, including a thyroid disorder, consider your own specific condition and talk to a doctor before you bring on the supplements. If you’re healthy, you can probably get everything you need from a balanced diet rich in a variety of plant and animal products.
Diet and the Thyroid: Other Factors
Micronutrients are one important part of the diet. But specific foods and other factors can also provoke thyroid problems – either because of their effects on the thyroid specifically, or because they exacerbate an autoimmune response in general.
One of the biggest contributors to thyroid problems is gluten. Since so many thyroid problems are either caused or exacerbated by autoimmune disease, gluten can contribute to thyroid dysregulation in general, by causing a leaky gut. Normally, the walls of the gut are impermeable, meaning that particles within the gut can’t just pass through them into your bloodstream. Foods like gluten can trick your intestinal walls into letting them through as well: this is called “leaky gut.” But even though your gut walls might be fooled, your immune system isn’t: it recognizes that gluten doesn’t belong in your bloodstream and attacks it. Unfortunately, this provokes a general autoimmune response throughout the body, causing your immune system to attack your own cells as well as the invading gluten.
Since thyroid problems are partly driven by immune dysfunction, the autoimmune element of leaky gut would be more than enough trouble for one protein to cause. But gluten is even more specifically tied to thyroid problems: gliadin, a protein in gluten, is chemically similar to the thyroid, so when the immune system makes antibodies against the gliadin, those same antibodies will prompt it to attack the thyroid. Studies have found that celiac disease is very strongly associated with autoimmune thyroid disorders, supporting this relationship and providing further evidence that people with thyroid problems should carefully avoid all gluten.
A high level of Polyunsaturated Fatty Acids (PUFAs) can also affect thyroid function – these fats cause inflammation, which damages the thyroid. As well as the specific foods you eat, the state of your gut flora can also affect proper thyroid function, because gut flora help convert T4 into T3. A poor balance of gut flora will make this conversion inefficient, and can contribute to a lack of T3 in the body.
Thus, although the dietary factors that affect thyroid function are highly complex and can’t be boiled down to any one “cause,” it’s clear that a basic, healthy paleo diet will go a long way toward supporting the health of your thyroid, as well as the health of every other part of you. There’s no need to hunt down any special “miracle foods” or go on an extremely strict elimination diet for thyroid problems: avoid gluten, PUFAs, and other toxins in general, support your gut flora with a healthy diet including probiotic foods, and enjoy the taste of real, nourishing foods.
Stress and the Thyroid
As if you needed another reason to avoid chronic stress, the health of your thyroid also depends on it! Stress is one of the environmental factors associated with the onset of autoimmune thyroid diseases like Graves’ and Hashimoto’s – probably because chronic stress contributes to leaky gut and causes chronic inflammation. Stress can also tie into to several of the other risk factors for thyroid disorders, including metabolic problems and blood sugar dysregulation. It seriously damages your gut flora, and interferes with proper function of the adrenal glands, causing problems for two organs responsible for regulating the thyroid: the hypothalamus and the pituitary. As if all of that weren’t enough, the chronic inflammation and hormone imbalances that accompany high stress levels interfere with the uptake of thyroid hormone and the conversion of T4 to T3.
Of course, “don’t be stressed” is much easier said than done, but the potential thyroid problems should only add to the list of reasons to turn off the TV and get to bed early, or take a day off once in a while to just relax and appreciate a long walk in the park and a good book. Even with shelves full of pills, powders, and supplements at your disposal and a thousand blogs full of new diet plans and nutrient-packed recipes, sometimes the best thing you can do for your health is to unplug and take a break.
Thyroid Hormone Replacement
Thyroid dysfunction is a complicated and many-faceted problem. While some people prefer to treat their thyroid exclusively with diet and lifestyle changes, many also turn to conventional medical approaches. The standard treatment for hypothyroid symptoms is hormone replacement, generally in the form of synthetic T4. This is helpful for many people, and if you find that the health benefits are more important than the side effects, hormone therapy can be a wonderful way to increase your quality of life. Also remember that this isn’t necessarily permanent: you might need replacement hormones as a “bridge” to help you get other diet and lifestyle factors under control, and then be able to leave the medications behind later.
One important caution to bear in mind with T4 replacement, though, is that it won’t help you if you have Euthyroid Sick Syndrome, or another problem that isn’t actually the result of thyroid dysfunction. If systemic inflammation is preventing your body from converting T4 to T3, it won’t matter how much T4 you take. In that case you’d need to take synthetic T3 directly.
In any case, it’s important to discuss your particular symptoms and condition with a doctor you trust. Since autoimmune conditions are so various, and since so many different environmental factors can influence thyroid symptoms, there is no one-size-fits-all recommendation for thyroid hormone therapy. And if you’re concerned about a doctor prescribing “healthy whole grains” and a low-fat diet, try the Paleo Physicians Network to find someone willing to work with your lifestyle choices, instead of against them.
Proper thyroid function is essential to overall health and well-being: autoimmune thyroid disorders can leave you too sick and run-down to enjoy your life, and ignoring them will only make the problem worse. While the causes of thyroid dysfunction aren’t completely understood, dietary and environmental stressors clearly play a role. This means that the Paleo prescription for thyroid health is the same as the Paleo prescription for everything else: eat a balanced diet of real food, avoid toxins, and minimize stress. If you do already suffer from thyroid dysfunction, a Paleo diet can help by eliminating several dietary factors that may be exacerbating your symptoms – it might not be a complete cure, but it’s a step in the right direction.
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