Poor sleep can affect almost every part of the body, including the hormones that keep us healthy. Researchers are increasingly finding that sleep disorders and hormone disorders often occur together.
A new Brazilian study suggests that one of the strongest links may be between hypothyroidism and obstructive sleep apnea.
Hypothyroidism develops when the thyroid gland in the neck produces too little thyroid hormone. These hormones help regulate how the body uses energy and influence many organs. When hormone levels fall, people may experience tiredness, slow thinking, constipation, weight gain, and other symptoms that can easily be mistaken for everyday fatigue.
Obstructive sleep apnea is also very common. During sleep, the muscles in the throat relax too much, causing the airway to narrow or close. Breathing repeatedly stops for short periods, reducing oxygen levels and interrupting sleep many times each night.
Researchers from the Federal University of São Paulo studied 761 adults from the EPISONO 2018 project to better understand whether these two conditions are connected. Participants completed laboratory tests and spent a night in a sleep laboratory where specialists measured their breathing, brain activity, oxygen levels, and other sleep signals.
The study found that hypothyroidism affected about one in eight participants. Among those with thyroid disease, almost one in two also had obstructive sleep apnea, a much higher rate than expected.
People with hypothyroidism experienced poorer sleep quality than other participants. They woke more frequently, had more interrupted sleep, and were more likely to have severe breathing problems while sleeping.
The researchers also discovered that higher levels of thyroid-stimulating hormone were linked to worse sleep apnea. At the same time, participants with more severe sleep apnea were more likely to have thyroid problems, suggesting that the relationship may work in both directions.
Treatment appeared to make a difference. Participants taking thyroid hormone replacement therapy slept almost 50 minutes longer than untreated patients. They also enjoyed more deep sleep, which plays an important role in restoring the body, strengthening memories, and supporting healthy brain function.
Even so, the researchers stress that treating hypothyroidism does not automatically cure sleep apnea. Both conditions can increase the risk of heart disease if left untreated, and each requires its own diagnosis and treatment plan.
The team hopes future studies will determine whether treating sleep apnea also improves thyroid function over time. Understanding this relationship could help doctors provide better care and improve quality of life for many patients.
The research was published in the journal SLEEPJ.
This study stands out because it included detailed overnight sleep testing instead of relying only on self-reported sleep problems. Its main limitation is that it cannot show which condition comes first. Even so, the findings strongly support a more complete medical approach in which patients with thyroid disease are evaluated for sleep disorders and patients with sleep apnea are checked for thyroid problems when appropriate.
Source: Federal University of São Paulo (UNIFESP).
