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What Happens If Hypothyroidism Is Left Untreated?

Learn about the risks associated with untreated hypothyroidism in this article.
What Happens If Hypothyroidism Is Left Untreated?
Last updated:
9/13/2026
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The Big Picture

An underactive thyroid affects nearly every system in the body, and when it goes untreated, either by choice or because it hasn't been diagnosed, the risks go well beyond the common symptoms of fatigue, weight gain, and brain fog. Untreated hypothyroidism has been linked to heart disease, including a higher risk of death in people who also have heart failure, as well as reduced kidney function and, in advanced cases, a goiter from the thyroid gland working overtime to compensate.

Left untreated for a long time, hypothyroidism can also progress to myxedema, a rare but life-threatening state where the body's metabolism slows so much it can lead to coma. It can affect fertility and pregnancy too, since healthy thyroid function plays a role in regular periods and reproductive hormone balance.

Not every case needs indefinite treatment. Some hypothyroidism related to pregnancy resolves on its own, and mild, subclinical cases may simply be monitored with repeat blood testing before medication is started. The key takeaway is that untreated hypothyroidism carries real risks, so working with a thyroid doctor to figure out whether, and how, to treat it is the safest path forward.

Over 20 million Americans live with a thyroid condition—and up to half don't even know it! 

The thyroid gland, located at the base of the neck, produces thyroid hormones that regulate the body's metabolism. Sometimes the body does not produce enough thyroid hormone. This condition is known as hypothyroidism. When thyroid hormone production drops, it affects virtually every system in the body. 

Common symptoms of hypothyroidism include:

Because an underactive thyroid affects so many different body systems, hypothyroidism is often confused with other conditions, or a diagnosis is missed entirely. In this instance, patients may be left untreated despite experiencing symptoms. 

Once diagnosed by a thyroid blood test, thyroid hormone replacement medication helps to treat hypothyroidism. We recommend you partner with a thyroid doctor to find the correct brand and dosage of thyroid medication. Once optimized, you should experience a reduction of symptoms.

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However, sometimes hypothyroidism is untreated, either due to choice or because the condition has yet to receive a diagnosis. So what are the risks associated with untreated thyroid conditions? 

What risks are associated with untreated thyroid conditions? 

Hypothyroidism left untreated can cause a host of more severe problems. 

Heart disease

When the thyroid gland makes insufficient thyroid hormone, it affects nearly every organ in the body—including the heart. Hypothyroidism can decrease cardiac output, resistance to blood flow, decreased arterial elasticity, and atherosclerosis (build-up in and on the artery walls). Impaired heart function due to hypothyroidism may lead to heart failure.

A 2013 study examines the risk of death between hypothyroidism and congestive heart failure. The study split patients into two groups: those with heart failure and those without heart failure. Results reveal that hypothyroidism significantly increases the risk of death among patients with heart failure compared to people with normal thyroid function. 

Kidney disease

Kidney disease is another possible result of untreated hypothyroidism. Thyroid hormones affect renal (relating to the kidneys) blood flow and the glomerular filtration rate (GFR). The GFR determines how well the kidneys filter blood. When the thyroid does not produce enough thyroid hormone, it may result in a reduced GFR. 

The GFR is reduced by about 40 percent in over half of adults with hypothyroidism. This reduction increases creatinine (a waste product produced by the breakdown of muscle cells) in the blood. It also increases the risk for diseases that affect muscle tissue. These changes are reversible with the treatment of hypothyroidism. 

Infertility

Healthy thyroid function is critical in reproduction and pregnancy. An underactive thyroid can cause irregular periods, hyperprolactinemia, or sex hormone imbalance—all of which may affect a person's ability to get pregnant.

Goiter

A goiter is an irregular enlargement of your thyroid gland. Several factors can cause a goiter, including but not limited to iodine deficiency, pregnancy, or hypothyroidism. When your thyroid does not produce enough thyroid hormone, your pituitary gland goes into overdrive to make an adequate amount of thyroid hormones. This overstimulation may cause the thyroid gland to enlarge. Small goiters that don't cause physical or cosmetic problems aren't a concern. However, large goiters can make it hard to breathe or swallow.

Myxedema

Myxedema is severely advanced hypothyroidism—when the disorder has progressed for a long time with no treatment. This life-threatening condition is rare because it's doubtful that you would ignore the symptoms and avoid treatment. Myxedema can eventually slow the body's metabolism to the point where you would fall into a coma. 

It's important to identify thyroid dysfunction early to prevent complications of hypothyroidism. If you suspect you have hypothyroidism, start with an at-home thyroid blood test to understand your thyroid function and what to do next. Hypothyroidism is manageable with the proper treatment.

           
           
             

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Is it ever safe not to treat hypothyroidism?

If your doctor has prescribed you thyroid medication for your thyroid condition, it is generally a good idea to follow their directions. However, in some cases, thyroid disorders may not need to be treated or at least not indefinitely, and your doctor will let you know. 

Hypothyroidism can occur during or after pregnancy. This maternal hypothyroidism may be temporary, and patients may be able to stop treatment shortly after giving birth when their thyroid hormone levels return to normal. Additionally, some individuals may have subclinical hypothyroidism, an early, mild form of hypothyroidism in which the TSH level is only a little bit above normal. In this instance, your doctor may wait to retest your blood levels before prescribing thyroid medication.

A note from Paloma Health



The outcome of not treating moderate to severe thyroid conditions can be severe and possibly life-threatening. We recommend you work with a trusted thyroid doctor to determine whether treatment is appropriate for you. 

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Frequently asked questions

What happens if hypothyroidism is left untreated?

Untreated hypothyroidism can lead to more serious problems over time, including heart disease, reduced kidney function, goiter, and in advanced cases, a life-threatening condition called myxedema.

Can untreated hypothyroidism affect my heart?

Yes. It can decrease cardiac output and arterial elasticity and contribute to atherosclerosis, and one study found it significantly raises the risk of death in people who already have heart failure.

Can untreated hypothyroidism cause a goiter?

Yes. When the thyroid doesn't make enough hormone, the pituitary gland pushes it to work harder, which can cause the thyroid gland to enlarge into a goiter.

Can untreated hypothyroidism affect fertility?

Yes. Healthy thyroid function plays a role in reproduction and pregnancy, and an underactive thyroid can cause irregular periods and hormone imbalances that make it harder to get pregnant.

Is it ever okay to not treat hypothyroidism?

In some cases, yes. Hypothyroidism related to pregnancy can resolve on its own, and mild subclinical hypothyroidism may just be monitored with repeat blood testing before starting medication, but this should always be a decision made with your doctor.

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Katie Wilkinson

Katie Wilkinson, previously serving as the Head of Content and Community at Paloma Health, fervently explores the nexus between healthcare and technology. Living with an autoimmune condition, she's experienced firsthand the limitations of conventional healthcare. This fuels both her personal and professional commitment to enhancing patient accessibility to superior care.

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