Hypothyroidism

Causes

What is thyroid deficiency and why does it matter?

Thyroid deficiency is the insufficient production of thyroid hormone, which can be transient or persistent. Most of the time, it is due to a problem within the thyroid gland. But less commonly, it can be the result of a problem with signaling molecules from the brain.  

Untreated hypothyroidism can play a role in issues with metabolism, high blood pressure, cholesterol, infertility, mental functioning, and nerves and muscles.

What are the causes?

The most common cause in the United States is chronic autoimmune (Hashimoto’s) thyroiditis, an autoimmune condition causing an antibody attack on the thyroid. Over time, this can destroy the thyroid gland.  

Other causes include surgical removal of the thyroid, radioactive iodine ablation for hyperthyroidism, radiation, iodine deficiency or excess, medications, and environmental exposures.

Does the underlying cause have any other treatment implications?

Some triggers of hypothyroidism are potentially reversible (such as nutrient abnormalities, medications, or early autoimmunity) while most will require lifelong medication.  

It is now thought that increased intestinal permeability is an important trigger in autoimmunity. If the intestinal integrity can be restored, it may improve autoimmunity and minimize the destruction of the thyroid gland.

Symptoms

What are hypothyroid symptoms?

The most common symptoms of hypothyroidism include cold intolerance and fatigue. Other common symptoms include joint pain, constipation, depression, difficulty concentrating, dry skin, thinning hair, hair loss, impaired memory, heavy periods, muscle aches, weakness and weight gain. Many of these are not specific to thyroid disease, making it difficult to diagnose by symptoms alone.

Who (if anyone) should be screened for thyroid disease even if they’re not having symptoms?

Unfortunately, there is no consensus among experts about whether to screen people without symptoms.

There is, however, agreement that screening should be done for patients with a history of autoimmune disease, a history of radioactive iodine therapy or head and neck irradiation, or a family history of thyroid disease. Screening is also recommended for those using medications like amiodarone or lithium, which impact thyroid function.

In addition, an evaluations can be worthwhile for those with psychiatric disorders, a history of thyroid surgery, and an abnormal thyroid exam in the office. Pregnant women should be evaluated as well.

Diagnosis

How is thyroid deficiency typically diagnosed?

After discussing symptoms and other relevant history, we use a blood test for diagnosis. Overt hypothyroidism, which is typically symptomatic, is diagnosed by a blood test showing elevated TSH (thyroid stimulating hormone) and low T4 hormone. Subclinical hypothyroidism, often asymptomatic, has an elevated TSH but a T4 hormone level in the normal range.  

What lab tests are important for initial diagnosis? What tests are important to follow over time?

TSH is the initial screening test, and free T4 should be measured if TSH is elevated. TSH is then followed to adjust medication once treatment is initiated. The normal range for TSH is controversial and can vary between laboratories. It also gradually increases with age.

What about the other lab tests? When (if ever) are they helpful?

Free T4 is helpful (and can help decide whether to treat) when the TSH is elevated in order to differentiate between overt and subclinical hypothyroidism. It can also be used when TSH is normal, but symptoms are significant.  

Testing free T3 can be helpful when T4 medication alone doesn’t fully relieve symptoms in order to determine if adding T3 to the regimen would be helpful.  

Testing for thyroid antibodies are particularly useful when investigating subclinical hypothyroidism or patients with thyroid gland enlargement in order to predict the likelihood of overt hypothyroidism in the future. It can also be used to confirm an autoimmune source of hypothyroidism and the level of autoimmunity present.

Reverse T3 doesn’t tend to change recommendations, so testing isn’t necessary.

Should people with thyroid deficiency have any imaging studies done?

Ultrasound of the thyroid is useful to further investigate a goiter or thyroid nodules. It doesn’t have a role in evaluating routine thyroid deficiency unless one of those features is present.

Treatment

Is one medication better than another?

Levothyroxine (Synthroid), or synthetic T4, is the recommended initial medication for treatment.  For most patients, it normalizes symptoms.

The addition of T3 may have a symptomatic benefit in some patients who do not achieve full remission of symptoms on T4 alone.

Some patients do best on natural dessicated thyroid which includes both T3 and T4.  

How is thyroid medication taken?

All thyroid medication should be taken on an empty stomach, 30-60 minutes before food or drink (other than water). Wait 4 hours after thyroid medication to take calcium, magnesium, or iron supplements as well as antacids.

Is there anything beyond medication that people can do to treat their thyroid?

A low gluten or gluten-free diet may prevent progression and complications of Hashimoto’s hypothyroidism. Also, small studies have shown that patients with lactose intolerance have improved thyroid function on lactose-free diets.

Correcting nutrient deficiencies of selenium, zinc, vitamin D, and iron may improve thyroid function or conversion of T4 to the more active T3 hormone.

Working with a practitioner to heal intestinal permeability may cause improvements in thyroid function by reducing thyroid autoimmunity.

Finally, because either too much or too little iodine can contribute to hypothyroidism, optimizing that status can be helpful. It’s also worth noting that insufficient iodine can cause healthy foods like broccoli and soy to depress thyroid function.  

What’s the “best level”? Is anywhere within the normal range good enough?

The goal when treating a patient with hypothyroidism is to relieve their symptoms without pushing them into hyperthyroidism. Any value within the normal range should avoid the complications of untreated hypothyroidism.

Within that range, some people may feel better at one end of normal or the other. Doctors will work with patients to achieve their optimal state of wellbeing while staying within a safe dosing range.

For women who are pregnant or trying to become pregnant, we recommend tighter thyroid control to prevent pregnancy complications (typically a TSH of 2.5 or less).

Some people report feeling better at lower levels of TSH; is there a risk to “over-treating”?

The greatest risks of over-treatment are bone loss and heart arrhythmias (irregular rhythm). Over-treatment is especially problematic in older patients or those with preexisting heart disease.

What other conditions change how people should be treated for thyroid?

Pregnancy, oral estrogen, weight gain, and a history of thyroid cancer will all change the need for thyroid hormone. Medications that interfere with thyroid hormone absorption or increase excretion can also have that impact.

What’s the best “whole person” approach to treating hypothyroidism?

Symptoms of hypothyroidism, ability to alter lifestyle, and response to treatment vary from person-to-person.

Initiating levothyroxine (T4) to relieve symptoms is a great place to start. It often takes a few weeks-to-months of adjusting the dose to find an optimal level as determined by symptom resolution and follow-up blood tests.  

Given the autoimmune nature of most thyroid disease, optimizing intestinal integrity and thereby hopefully reducing autoimmunity rounds out the long-term treatment. This may involve nutritional support, dietary change, stress management, or other lifestyle changes.

Working with a practitioner to find your optimal lifestyle and medication approach is the best way to feel energetic and back to yourself as quickly as possible.

Useful Links

Updated guide for diagnosis and treatment (American Family Physician)

Helpful integrative treatment guide (University of Wisconsin Department of Family Medicine)

Overview of recommendations (American Thyroid Association)

Technical review of Hashimoto’s connection to intestinal changes (Endocrine Connections)