Why did I get thyroid disease?
This is a question anyone with a new diagnosis of thyroid disease will naturally ask. I hear it several times each week in my practice. I think it is important to understand for several reasons.
One is just intellectual curiosity. When things go wrong, we want to know why in order to have some sense of understanding and control. Without it, we are left unsure of what else might go wrong unexpectedly.
Another is prevention. If this happened to you, what can you learn that might help prevent your loved ones from experiencing it?
One of the most useful reasons for understanding why you have thyroid disease is this: By knowing how it happened, the steps that will help you feel better become more apparent.
Thyroid disease is primarily an immune disease. In this post, I'll explain why your immune system attacks your thyroid. In the next, I'll explain the most common ways this plays out, namely Hashimoto's thyroiditis and Graves' disease.
To understand how your thyroid can go wrong, let me first explain a few key concepts related to it, your immunity and your genes.
Your thyroid needs iodine in order to function. At first glance, that does not seem too unusual. Many parts of your body need nutrients to work right. In some ways, however, this relationship is different. As best we can tell, your thyroid is the only part of your body that needs iodine. This is unusual. Every other nutrient we know of is used for many body processes with a large variety of reactions.
Another unusual thing about iodine and your thyroid is that it needs a pump. All of the other nutrients our body uses are found in adequate amounts in our bloodstream (assuming we are not deficient). Your bloodstream cannot carry enough iodine for a thyroid, so your thyroid has a pump that pulls iodine inside of it at concentrations up to 100 times what is found in the blood. This pump can be part of the problem, leading to thyroid disease because it can pull toxins inside your thyroid, along with the iodine. Ironically, the best-documented toxins to trigger thyroid disease not only include iodine itself, but also perchlorate, lead, mercury and over 200 other environmental chemicals. 
The other player involved in this response is your immune system. Overall, your immune system acts like a home security guard. Its job is to keep dangerous bacteria, viruses and fungi from getting inside your body and hurting you. Imagine a home security guard attacking your mail carrier. When the guard attacks something from outside of you that is not dangerous, we call this an allergy. Imagine the security guard attacking your pet by mistake. Your pet is harmless, and it's supposed to be inside your home. When your immune system attacks something that is supposed to be inside of you, we call this an autoimmune reaction. In most cases, you are better off when your immune system attacks something unnecessary rather than when it ignores something dangerous. Allergies may be a nuisance, but they are better than letting bacteria create septic shock. If your home security guard was overworked and had a high stress load, he may be more apt to attack the wrong things. It is also true that your immune system is more likely to make mistakes when it has more stress, like ongoing infections, allergies or problems in the intestinal tract.
Your thyroid gland is an interconnected part of your endocrine system. Each gland in the system has a distinct rule, yet they also interact with one another. The glands that have the most ties with your thyroid include the ovaries and the adrenals. This is one of the reasons women get more thyroid disease than men. When the adrenal glands change their output of stress hormones, this can both stress the immune system and make your cells not absorb thyroid hormones properly. The ovaries produce estrogen, which causes your liver to make proteins that weaken the thyroid hormones. Because of this, anytime there is a big change in the ovaries, it can cause the thyroid strain. These times include pregnancy, perimenopause, and menopause.
The last part of this equation is your genetic makeup. The data is very strong that disease runs in families. This happens because toxins are part of the chain of events that trigger thyroid disease, and there are genes that determine how effectively you can detoxify your body. We are all exposed to countless chemicals each day. Some have estimated there are over 3 million new chemicals in our environment since the 1900s . You can think of your genetic ability to detoxify as how stain-resistant a fabric is. With some fabrics, you can spill pasta sauce or berries and know they will rinse right off. With others, it will be stained forever by the same foods. Even though we are all exposed to toxins, some of us are apt to have more of those toxins stay inside of us than others.
Now that you understand the players, here's how it all can produce the perfect storm that leads to thyroid disease:
Step one: You have some degree of genetic susceptibility to thyroid disease. Choose your parents wisely.
Step two: Your body is exposed to chemicals that can be concentrated within your thyroid. These build up inside the thyroid and create chronic inflammation.
Step three: Fluctuations in hormones from your ovaries or adrenals may cause strain on your thyroid.
Step four: Some stressor to your immune system, like an infection, an airborne allergy or a food reaction, causes it to become too aggressive.
Step five: Your immune system now starts to attack your thyroid.
Understanding these steps is helpful to reduce your risk of thyroid disease. For those who have thyroid disease, understanding these steps should help you understand the steps that should be taken to regain your health.
In the next edition to this article, I will discuss the most common effects this attack against your thyroid can have and what practical steps you can do to improve your health.
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Gupta P, Kar A: Role of ascorbic acid in cadmium-induced thyroid dysfunction and lipid peroxidation. J Appl Toxicol 18:317-20,1998.