Can fixing my thyroid cure my sleep apnea?

Sometimes, but not reliably. In a 1984 study, apnea events dropped by about 80% on thyroxine, while in a 1988 report most patients still had apnea after their levels were normal. A repeat sleep study is the only way to know if your apnea is gone.

Does subclinical hypothyroidism cause sleep apnea?

There is no clear evidence that it does. Subclinical hypothyroidism is common in people with OSA, with rates around 8% to 11% in published studies, but that does not show it causes the apnea. Weight and age often explain both.

Why does hypothyroidism make me snore?

Low thyroid hormone can cause swelling of the tongue and throat tissues and weaker airway muscles. Both narrow the airway, which makes the tissues vibrate as you breathe. In one study, all 20 hypothyroid patients snored.

Is daytime sleepiness from my thyroid or from sleep apnea?

It can be either, or both. Fatigue and sleepiness are common to both conditions, so symptoms alone cannot tell them apart. If you snore loudly or someone sees you stop breathing at night, ask about a sleep study.

Can sleep apnea cause hypothyroidism?

The evidence for that direction is weak. A 2024 genetic study found no causal effect of OSA on hypothyroidism, although a 2025 study reported one for a specific subgroup. The main concern is the thyroid affecting the airway, not the reverse.

Can Hypothyroidism Cause Sleep Apnea?

The short answer: It can. An underactive thyroid can narrow the upper airway and weaken the drive to breathe, and both raise the risk of obstructive sleep apnea (OSA). Small studies found apnea in most people with untreated, severe hypothyroidism. Levothyroxine often reduces apnea but does not always cure it, and most people with OSA have a normal thyroid.

How can an underactive thyroid affect breathing during sleep?

Obstructive sleep apnea happens when the upper airway collapses or gets blocked during sleep. The National Heart, Lung, and Blood Institute lists low levels of thyroid hormones among the hormone changes that raise the risk. Researchers describe several ways this can happen:

Tissue swelling in the airway. A 2022 study in the Annals of African Medicine describes mucopolysaccharide buildup in the hypopharynx, tongue, and other tissues. This is the same process that causes the puffy face of myxedema. It can crowd the throat.
Weak airway muscles. In a 1988 report of 10 patients, doctors found hypothyroid muscle weakness in the upper airway as one likely cause.
Weaker drive to breathe. A 1984 study in the Annals of Internal Medicine found that breathing effort against resistance increased once patients took thyroxine. A 1992 study in Chest also found impaired respiratory drive that thyroid hormone corrected.
Weight gain. Hypothyroidism can add weight, and extra fat in the neck narrows the airway. Our guide to thyroid and weight changes covers how much weight is realistic to expect.

MedlinePlus lists hoarseness and a puffy face, hands, and feet as late signs of untreated hypothyroidism. Those signs point to the same tissue changes.

How common is sleep apnea in people with hypothyroidism?

The answer depends on how severe the thyroid disease is. The early studies looked at people with new, untreated disease:

In the 1984 study, 9 of 11 newly diagnosed patients had sleep apnea. The obese patients averaged 99.5 episodes per hour, versus 16.3 in the patients who were not obese.
In the 1992 Chest study, 5 of 20 hypothyroid patients had OSA (2 moderate to severe, 3 mild). Every one of the 20 snored.
In a 2022 study from India, 74 of 100 hypothyroid patients had OSA on an overnight sleep study. OSA was found in 85.3% of untreated patients and 66.1% of treated patients.

These are small hospital samples, and many patients were overweight. The strongest population data come from the United States. An analysis of 5,515 adults in the NHANES 2007-2008 survey found that hypothyroidism was linked to 1.88 times the odds of sleep apnea. That held after adjusting for body mass index, smoking, alcohol, and other conditions. The sleep apnea diagnosis in that study was self-reported, which is a limit.

Is it cause and effect, or just overlap?

The evidence points both ways, and weight makes it hard to separate the two conditions. A 2016 meta-analysis found that people with OSA and hypothyroidism had worse apnea scores and more time with low oxygen than euthyroid OSA patients. The authors warned that obesity could be a confounder.

A 2023 meta-analysis of 23 studies in Medicine reached a cooler view. It found no significant correlation between apnea severity and TSH, free T4, or free T3. The authors called the relationship controversial.

Genetic studies add some support for a real effect. A 2024 Mendelian randomization study found that genetically predicted hypothyroidism raised the odds of OSA (odds ratio 1.734). It found no effect in the other direction. This method reduces confounding, but it does not prove that treating the thyroid fixes the apnea.

Does levothyroxine improve sleep apnea?

Often it helps, but not for everyone. The results from the small studies differ:

In the 1984 study, apnea fell from a mean of 71.8 to 12.7 episodes per hour after 3 to 12 months of thyroxine. Body weight did not drop.
In the 1988 report, 6 of the 8 patients followed up still had sleep apnea after their thyroid levels were normal. Their mean apnea index barely moved, from 51 to 45.
In the 1992 study, respiratory drive improved, but snoring corrected only after one year of therapy.

The American Academy of Sleep Medicine (AASM) 2009 adult OSA guideline says there are no widely effective drug treatments for OSA except in people with hypothyroidism or acromegaly. Treating those conditions can improve the apnea-hypopnea index (AHI).

There is one safety point. In the 1988 report, two patients developed nighttime chest pain and heart rhythm problems after starting thyroxine, even at low doses. CPAP stopped those events. That is why doctors sometimes treat both conditions at the same time.

Should people with sleep apnea get a TSH test?

No major guideline tells doctors to test thyroid levels in every person with OSA. The AASM 2009 guideline covers the history, exam, and sleep testing for OSA. It does not call for routine thyroid tests. A 2016 review noted the lack of international guidelines on the question. Its authors still argued that TSH screening might help most OSA patients.

The data on routine screening are thin. In a 1996 study of 255 people sent for sleep testing, only 1.6% had hypothyroidism. The rate in people with OSA (2.9%) was not significantly different from people without it (0.7%). The authors advised testing only when there are thyroid symptoms or in high-risk groups, such as women over 60. A 2011 study of 271 OSA patients found new overt hypothyroidism in just 0.4%, but subclinical hypothyroidism in 11.1%. Mild, subclinical cases are common, and they are a separate question. See our guide to subclinical hypothyroidism.

In practice, a TSH test makes sense if you have OSA plus other thyroid signs. These include cold intolerance, dry skin, constipation, a slow pulse, or a goiter. It also makes sense if your OSA seems out of proportion to your weight.

What should you do if you have both?

Treat each condition on its own terms. Take levothyroxine as prescribed and have your TSH checked as your doctor advises. Do not assume that a normal TSH means your apnea is gone. Ask whether a repeat sleep study makes sense once your thyroid levels have been stable for several months.

Keep using CPAP or your prescribed treatment unless a sleep specialist tells you to stop. Watch for loud snoring, gasping at night, morning headaches, and daytime sleepiness. Those symptoms overlap with hypothyroid fatigue, so they are easy to blame on the thyroid alone. If sleep problems persist, our sister site insomnia.md covers other causes of poor sleep.

The bottom line

Hypothyroidism is a known, treatable contributor to obstructive sleep apnea. It works through airway swelling, weak airway muscles, reduced breathing drive, and weight gain. Levothyroxine can cut apnea sharply in some people, but many still need CPAP after their levels are normal. Routine thyroid testing for everyone with OSA is not guideline-backed, but a TSH test is reasonable when thyroid symptoms are present. For the full symptom list, see our guide to hypothyroidism warning signs.

Last updated: September 2026. This article is for informational purposes only and does not constitute medical advice. Talk with your doctor or a sleep specialist before you start, stop, or change treatment for sleep apnea or your thyroid.