Stop Blaming Weight Gain on Your Thyroid

When your immune system fights back…

… and your thyroid is in the crosshairs

What is Hashimoto’s?

Hashimoto’s disease, also known as Hashimoto’s thyroiditis or chronic lymphocytic thyroiditis, is an autoimmune disease in which your immune system attacks your thyroid. It is estimated that Hashimoto’s affects about 5% of the population at some point in their life, or 1 in 1000 people at any point in time.

The thyroid is part of the endocrine system which produces hormones important for many of the body’s functions, primarily influencing metabolism and protein synthesis but also plays a role in calcium homeostasis. The thyroid makes two thyroid hormones, T3 (triiodothyronine) and T4 (thyroxine), from iodine and the amino acid tyrosine. T4 acts as a prohormone or reservoir for the more active form, T3. T4 is converted to T3 as needed.

Inflammation from Hashimoto’s often leads to hypothyroidism, also called underactive thyroid. Hashimoto’s is actually the most common cause of hypothyroidism in the US and affect mostly middle-aged women (30-50 years of age) but can occur in both sexes and at any age. This is not surprising since autoimmune disorders are more common in females than in males. People who have family members with thyroid or other autoimmune diseases are also at higher risk.

So, while Hashimoto’s can cause hypothyroidism, they are NOT THE SAME. Hashimoto’s is a disease. Hypothyroidism is a condition.


How do I know if I have Hashimoto’s?

You might not have any signs or symptoms at first. Hashimoto’s usually develops slowly over several years. An enlarged thyroid, or goiter, is usually the first sign.

Symptoms of an underactive thyroid may include: fatigue, weight gain or difficulty losing weight, pale or puffy face, sensitivity to cold, joint and muscle pain, dry skin, constipation, brittle nails, dry or thinning hair, depression, slowed heart rate, problems getting or staying pregnant, or heavy or irregular periods.

If suspected, your doctor will do an exam and order some tests:

Thyroid function tests use a blood sample to analyze levels of TSH (thyroid stimulating hormone) and thyroid hormone (T4) in your blood. Elevated TSH levels are an indication of an underactive thyroid. However, you may still go undiagnosed with what is termed “subclinical hypothyroidism” in which your TSH levels are slightly higher than normal and T4 levels are normal. Eventually, the thyroid will not be able to keep pumping out thyroid hormone and T4 levels will drop below normal. You may also have levels of T3 tested. If you are unable to convert T4 to the more active T3 form, this may not show up in the regular TSH or T4 tests. Much commonly tested is thyroglobulin (Tg) level. Tg is a protein that is used by the thyroid to make T3 and T4 hormones and is not a primary measure of thyroid hormone function. It is used mostly as a tumor marker for thyroid cancer treatment.

Antibody tests use a blood sample to look for elevated levels of anti-thyroid peroxidase antibodies. Many with Hashimoto’s will have specific antibodies that people with other causes of underactive thyroid do not have. However, just because you have antibodies present does not mean that you will have any symptoms – thyroid function may still be normal. Patients with elevated antibody levels but normal thyroid function do not require treatment.

Radioactive iodine uptake tests are not blood-related. T4 contains iodine and the thyroid must take a large amount of iodine from the blood in order to make an appropriate amount of T4 hormone. Because of this mechanism, doctors can track where a swallowed radioactive sample of iodine goes in the body. By measuring the amount of radioactive sample taken up by the thyroid, doctors can determine if the gland is functioning normally. A high uptake is associated with an overactive thyroid (hyperthyroidism) and a low uptake is usually associated with an underactive thyroid (hypothyroidism). A thyroid scan may also be done to show a picture of the thyroid gland.


How is it treated?

Hashimoto’s is usually treated clinically with the drug levothyroxine (Levoxyl, Synthroid, Levothroid), which is synthetic T4 thyroid hormone, in what is called thyroid replacement therapy. Most people will need to be on this for the rest of their life, but the dose may change. Less commonly used, desiccated thyroid hormones (Armour Thyroid or Nature-Throid, from pig thyroid glands) are a more “natural” treatment, and combination T3/T4 (Thyrolar) and pure-T3 (Cytomel) medications may also be used. Many report feeling best when taking both replacement T3 and T4, rather than just T4 alone.

Prior to the development of levothyroxine, desiccated animal thyroid extract was the only available treatment for hypothyroidism. In one recent study, it was shown that patients prefer taking desiccated thyroid extract and it was associated with more weight loss. There was also no difference in psychometric testing or in symptoms and both types of treatment normalized thyroid blood test results.

In the beginning of treatment, TSH levels may be tested every 6-8 weeks until appropriate dosage has been determined. After that, testing once a year is usually sufficient.

If left untreated, underactive thyroid can cause infertility, miscarriage, birth defects, high cholesterol, heart failure, seizures, coma, or even death.

Diet and Nutrition

Because of the observed connection between gluten, dairy, and autoimmune disease, you may want to try going gluten- and dairy-free, at least for a trial period. Try completely avoiding gluten and dairy for 30 days and see if your symptoms improve. Gluten and dairy can both be inflammatory for many people. The -itis part of “thyroiditis” stands for inflammation. The Paleo diet would be an example of a gluten- and dairy-free eating pattern.

You may even want to try a full-blown elimination diet to pinpoint other foods which may be causing inflammation, like soy or corn or tomatoes. Be warned, elimination diets require a very detailed protocol and reintroduction system that can take months if not a year to fully complete.

Research is still lacking and there is no official Medical Nutrition Therapy diet for Hashimoto’s, so much of the information online and in diet books today is largely anecdotal.

Focus on healthful behaviors rather than on the numbers on the scale. I think that dietitians can agree that a diet emphasizing more vegetables, lean protein, healthy fats, high-fiber foods, and fluids and minimizing sugar, added fat, and processed foods is fundamental for everyone.

Both nutrient deficiencies and excesses can trigger or worsen thyroid symptoms. Key nutrients like iodine, vitamin D, vitamin B12, and selenium have been linked to thyroid health.


This is probably the topic most hotly debated in regards to thyroid health and nutrition. Cruciferous vegetables, like broccoli and cabbage, contain a compound called goitrin when they are broken down. Goitrin can interfere with the production of thyroid hormones, but this is usually only a concern when coupled with an iodine deficiency. Don’t worry, though! Cooking denatures most, if not all, of the potential goitrogenic effect.

Soy is another potential goitrogen. However, studies have shown that it does not cause hypothyroidism in those with adequate iodine intake. Millet, a naturally gluten-free grain, may potentially also suppress thyroid function even in people with adequate iodine intake. But, really, how often are you eating millet?



Thyroid medications have the potential to interact with common foods and supplements, such as calcium, coffee, and fiber. These decrease the absorption of the medication and therefore the effectiveness of the medication. Calcium should be taken at least four hours apart from medication and coffee and fiber supplements at least one hour apart. This is only a short list, many more may interfere so proceed with caution. Certain herbs may also interfere with medications. Always check and let your doctor know what you are taking, regardless of whether you consider it a “medication” or not!


Since metabolism is lower in individuals with hypothyroidism, it is usually associated with weight gain, with greater weight gain in those with more severe hypothyroidism. However, this decrease in metabolism is usually quite modest. The cause of weight gain is complex and not always related to excess fat gain. Most is actually due to excess salt and water accumulationMassive weight gain is rare. In general, 5-10 pounds of body weight can be attributed to thyroid hormone levels, depending on severity.

If weight gain is the only symptom present, it is less likely that the weight gain is solely due to thyroid function.

After proper treatment, expected weight loss is small, usually less than 10% of starting weight. Additionally, since development of hypothyroidism is usually slow, many do not experience any significant weight loss after treatment.

Once thyroid hormone levels have returned to the normal range, the ability to lose or gain weight is the same as someone who does not have thyroid problems.


Inflammation and autoimmune disease cause a lot of chronic stress on the body, so it would be a good idea to cut down on external stressors wherever we can.

Get enough sleep (7-9 hours every night), expose your skin to direct sunlight (or supplement with vitamin D if you are deficient), eat real foods (less processed foods, more produce), move your body (don’t overexert yourself, start with walking or yoga), and take time every day to meditate and relax (even if it’s just 5 minutes). You might also consider taking a probiotic – the majority of your immune system is actually found in your GUT!

Have you been diagnosed with Hashimoto’s disease?
What has been working for you?