Subclinical Hyperthyroidism Explained

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Not feeling like yourself? Your thyroid may be to blame

Your thyroid is a small gland located toward the front of your throat, a few inches beneath your chin. This gland performs many functions, like controlling your body temperature, metabolism, and heartbeat. Basically, it controls how your body uses energy. 

The thyroid works with other hormone-producing glands in the body, especially the hypothalamus and pituitary gland in the brain. These glands constantly monitor hormone levels, and they prompt the thyroid to release more or less thyroid hormone depending upon the current concentration circulating.

An overactive thyroid gland can make these functions go faster, while an underactive thyroid can make them move more slowly. Either way, people with thyroid conditions likely don't feel as healthy as they used to. 

If you haven't been feeling like yourself for a few months, it might be time to see your doctor and ask about getting your thyroid tested. 

What is hyperthyroidism?

Hyperthyroidism is a condition in which your thyroid produces too much thyroid hormone. Excessive thyroid hormone can negatively impact many other parts of the body like your heart, bones, and muscle function, and its associated symptoms get worse without treatment. 

Symptoms of hyperthyroidism

Hyperthyroidism presents itself differently in everybody, but there are a set of common symptoms associated with the condition. Some common symptoms of hyperthyroidism include:

People with hyperthyroidism often feel initially energized, but this can quickly lead to excessive fatigue if left untreated. All of these symptoms can make it difficult to carry out normal daily tasks, but with proper treatment, people with hyperthyroidism can live long, healthy lives

Causes of hyperthyroidism

Although high thyroid hormone levels cause the symptoms associated with hyperthyroidism, the condition itself has many possible causes, such as:

  • Thyroiditis: Inflammation of the thyroid

  • High iodine intake: found in medications, supplements, and foods that contain seaweed

  • Thyroid nodules: Growths that can prompt the thyroid to make too much thyroid hormone

  • Graves’ disease: An autoimmune condition that confuses your immune system, making it attack your thyroid 

  • Too much thyroid medication: This sometimes happens when people are prescribed thyroid hormone medicine for hypothyroidism

In many cases, those who develop hyperthyroidism already deal with other conditions that negatively affect thyroid function. In others, hyperthyroidism can seem to come out of nowhere. Either way, getting appropriate medical intervention is necessary for helping you feel better. 

Risk factors for hyperthyroidism

Approximately 1 in 100 Americans over the age of 12 have hyperthyroidism. Some of the most common risk factors for hyperthyroidism are:

  • Being a woman

  • Being over 60 years old

  • Having an autoimmune disease

  • Having a family history of thyroid disease, especially hyperthyroidism

  • Using nicotine products

  • Ingesting large amounts of iodine, either from food or medications

If you are concerned about your thyroid function, and you also have one or more of the above risk factors, you should make an appointment with your doctor to discuss the possibility of having hyperthyroidism. Prompt medical intervention can help you return to feeling normal, or you can get peace of mind if your doctor can safely rule it out.

Interestingly, some people have thyroid issues and experience mild symptoms, but their thyroid levels remain within normal ranges. This is referred to as subclinical hyperthyroidism. 

What is subclinical hyperthyroidism?

Subclinical hyperthyroidism can be described as a mild form of overt hyperthyroidism, as people with subclinical hyperthyroidism either have mild symptoms or no detectable symptoms at all. The word ‘subclinical’ means a condition not severe enough to produce observable symptoms or warrant treatment, while ‘overt’ means readily apparent or obvious. 

Doctors don't often test patients for subclinical hyperthyroidism unless they have bothersome symptoms like those mentioned above. If blood thyroid hormone tests are carried out, patients with subclinical hyperthyroidism tend to have low levels of thyroid-stimulating hormone¹ (TSH) but normal levels of T3 and T4 hormones. 

Is subclinical hyperthyroidism dangerous?

No, subclinical hyperthyroidism doesn't usually pose a severe threat to a person's health and well-being, though current evidence¹ shows that subclinical hyperthyroidism is associated with atrial fibrillation, or irregular heartbeat. It can also increase the risk of developing overt hyperthyroidism in the future.

Fortunately, health risks commonly associated with overt hyperthyroidism, like heart problems and bone fractures, aren't strongly associated with subclinical hyperthyroidism, so most doctors don't test for it regularly, and often don't provide treatment if they detect it. There are some exceptions to this rule, however. 

Who gets treated for subclinical hyperthyroidism?

Your doctor may provide treatment for subclinical hyperthyroidism if you have moderate to severe symptoms despite not testing outside of the normal range for T3 and T4 hormones.

It is also recommended that physicians treat adults over 65 years old¹ with subclinical hyperthyroidism to prevent atrial fibrillation, as well as postmenopausal women with osteoporosis and TSH levels of 0.1mIU per L to prevent further bone loss. 

If you think you might have subclinical or overt hyperthyroidism, you should speak with your doctor. They will ask you about your symptoms, gather information about your family history, and perform a physical exam to look for signs that your thyroid is not functioning properly. If your doctor believes you may be at risk of hyperthyroidism, they will order a thyroid hormone blood test.

Depending upon your results, your doctor may suggest treatment options, and they will work with you to create a comprehensive treatment plan. Alternatively, your doctor may opt to monitor the situation for the foreseeable future.

Many people with subclinical hyperthyroidism overcome the condition without medical treatment,² but you should continue to closely monitor your symptoms and get regular checkups to ensure that your thyroid issues aren't getting worse. 

Treatment options for hyperthyroidism

If your doctor believes you need treatment for subclinical hyperthyroidism, or your subclinical hyperthyroidism has transitioned to overt hyperthyroidism, there are a few treatment options that can make you feel better and improve your quality of life. 

Antithyroid medications

Antithyroid medications stop your thyroid from producing new thyroid hormones, and this can help bring your circulating thyroid hormone levels back down to normal. You should start to feel better after 6 to 12 weeks once you start medication.

Most people with hyperthyroidism can be on antithyroid medication temporarily, usually for 12 to 18 months. 

Relapse is possible, so your doctor may have to re-prescribe the medication if your thyroid hormone levels rise above normal again.

Radioactive iodine

If your body doesn't respond adequately to antithyroid medications, your doctor may prescribe radioactive iodine. Radioactive iodine is taken by mouth as a tablet, and it gets absorbed by your thyroid.

This causes your thyroid gland to shrink, forcing it to produce less thyroid hormone over time. Your body gets rid of the radioactive iodine after just a few weeks. 


Although beta-blockers are typically prescribed to people with abnormal heart rhythms, some doctors prescribe them to people with hyperthyroidism to help with certain symptoms.

Because people with hyperthyroidism often have an elevated heart rate, they also often experience anxiety and tremors, which beta-blockers can help with. Once your thyroid levels return to baseline, you should be able to stop taking them. 


Some people's symptoms may not improve enough with the above treatments, or they may have a goiter that makes breathing difficult, so their doctor may recommend a thyroidectomy. 

Thyroidectomies involve removing some or all of the thyroid gland. The surgery usually only takes a few hours at most, and many people can go home on the same day. Patients who have their entire thyroid removed during the process will need to take supplemental thyroid hormone for the rest of their life. 

When it comes to subclinical hyperthyroidism, your doctor will most likely stick to antithyroid medication and radioactive iodine unless your thyroid hormones move into overt hyperthyroidism territory. 

The lowdown

Thyroid issues can cause a whole host of problems throughout the body, and it can be overwhelming to deal with numerous symptoms that make you feel unwell. It can also be frustrating to receive a diagnosis of subclinical hyperthyroidism, as you might not be given treatment for your condition as you would with overt hyperthyroidism.

When this happens, you may be tempted to look at home remedies for restoring your thyroid hormone levels, but it's always best to rely on your doctor to get the best evidence-based advice on taking care of yourself with overt or subclinical hyperthyroidism.

  1. Subclinical hyperthyroidism: When to consider treatment (2017)

  2. Management of subclinical hyperthyroidism (2012)

Other sources:

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