How Thyroid Stimulating Hormone (TSH) Works
TSH is the messenger molecule that goes from the pituitary gland to the thyroid gland to tell the thyroid to make more thyroid hormone, thyroxine (T4). T4 is then converted to T3, which is the active thyroid hormone.
TSH is produced by the pituitary gland, which is located at the base of your brain. The hypothalamus reads the amount of TSH in the blood, and when levels start dropping, it sends a signal to the pituitary gland. The pituitary then tells the thyroid to make more T4. When the TSH goes up, that typically means the thyroid is hypo and slowing down. If TSH goes down on its own, that’s hyperthyroid.
What Is a Thyroid-Stimulating Hormone Test?
A TSH test measures the amount of TSH in the blood. Testing only TSH is fine if the signaling is working well, but if it’s not, TSH isn’t the whole thyroid picture and other thyroid labs should be drawn.
TSH ideal value: 0.5-1.5
Lab Tests Related to Thyroid Function
Free T4
The thyroid makes T4 and it gets converted to T3, the active form. T4 effects brain, lungs, and heart.
Ideal value: 1.3-1.6 ng/dL
Free T3 (the active form)
T3 stimulates the contraction of the left heart ventricle. A healthy cardiac output indicates optimal left ventricle function.
T4 effects brain, lungs, and heart. T3 effects those and everything else.
Ideal value: 3.5 ng/dL or higher (a lab range is 2.3-4.2)
What Can Make TSH Levels Increase?
When the thyroid starts to slow down, TSH levels increase. This isn't a good thing. What could be causing this slow down in thyroid function?
1. Genetics
There’s a genetic component to low thyroid function.
2. Toxic metals
Mercury has a profound effect on the thyroid gland, but Aluminum, Cadmium, Lead, and Arsenic also negatively effect it. The active thyroid hormone (T3) is produced in the liver, so for T4 to be converted to T3, you need a good, healthy liver. Here are some simple suggestions for optimal cleansing. If you want to know whether your body is harboring heavy metals, I highly recommend a hair mineral analysis! It's worth its weight in gold and can reveal exposure to 7 different heavy metals, thyroid function, adrenal function, and how the body manages and uses insulin.
Heavy metals compromise the actual sufficient production of T3. Mercury binds to selenium, which plays a major role in converting T4 to T3, but if your body is high in mercury, the body allocates selenium to remove the toxins and ignores the conversion of T4 to T3. Mercury is very toxic and also contributes to mitochondrial dysfunction. It's best to supplement with a high quality selenium supplement to restore healthy concentrations of selenium.
3. Birth Control Pills
4. Estrogen Dominance
Estrogen dominance is such a prominent problem these days, and too much estrogen in the body slows down the thyroid -- this includes estrogen replacement therapy and hormone disruptors, like xenoestrogens. The hormone estrogen is cleared by the liver, and you must have regular bowel movements to eliminate it fast enough. Keep your liver healthy and your bowels moving!
Iodine deficiency also leads to estrogen dominance. Kelp is an excellent chelator of estrogen and also a source of iodine.
On the flipside, bio-identical progesterone supports healthy thyroid function.
5. Environmental Xenoestrogens
Exposure to anything plastic, fertilizers and pesticides, radiation and pollutants have been known to increase a person's risk of developing thyroid problems (and so many more problems!). The Environmental Working Group is an amazing resource for learning more about xenoestrogens and the most common ones in our environment. Three of the most prevalent xenoestrogens in our daily lives are Bisphenol A (BPA), Phthalates and Parabens.
When it comes to avoiding pesticides and herbicides on your food, it helps me to refer to the Environmental Working Group's Dirty Dozen and Clean Fifteen list.
6. Chlorinated and Fluoridated water and Fluoride treatments
The thyroid gland has a natural high affinity for halogens and metals. While this affinity is intended to draw iodine (halogen) and selenium (a metalloid) into the thyroid for the production and metabolism of thyroid hormones, it can also lead to the accumulation of harmful halogens and metals within the gland. Chlorine and flouride are two halogens harmful to the thyroid gland and they displace the iodine, which is essential for thyroid hormone function.
7. Bromine
There's a chemical call Potassium Bromate and it's commonly used when making processed grains (Potassium Bromate is how its listed on a food label in the ingredients). This ingredient is added as part of the bread-making process and it is anti-iodine. This means it strips iodine from the body, which is bad since iodine is essential for thyroid function. Bromine does this by displacing iodine from the thyroid hormones.
T4 is the major thyroid hormone manufactured by the thyroid gland and it contains four iodine atoms. The bromine knocks those iodine’s off and replaces them with bromine, and turns T4 unfunctional -- this means T4 can’t do its job of converting to active T3.
What foods contain Bromine? Many soft drinks, farm-raised fish, deli meat, some peanut butter, coloring agents, brominated vegetable oil, baked goods made with bromated flour (ie: pizza dough)
8. Gut Dysbiosis
Gut health is foundational to thyroid health. Since most of the immune system is located in your gut, poor gut health is a significant factor in triggering autoimmune diseases such as Hashimoto's (the body makes antibodies against the thyroid). And vice versa, appropriately managing and restoring thyroid function can help improve digestive function. Studies also show hypothyroidism can cause intestinal permeability, or "leaky gut," which allows undigested food into the bloodstream which instigates an immune attack. If you think you have leaky gut, check out the Institute for Functional Medicine's 4R program for dealing with Leaky Gut.
The zillions of bacteria living in your body mastermind your health in amazing ways. Learn how to get the bacteria in your microbiome working for, not against, you. The bacteria in your gut also effect body weight, appetite and mood! These are my favorite gut nourishers to support your overall health and your thyroid function.
Kelly Harrington, MS, RDN
Registered Dietitian Nutritionist for Healthy Goods
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