This is the medical term for an underactive thyroid. If you suspect you might have an underactive thyroid, it’s best to see your GP who can run blood tests. Ellen Maria Sampaio Xerfan, the study’s lead author, said: “We expected the prevalence of sleep apnoea to be considerable among people with hypothyroidism, but the result was higher than we’d imagined. AdvertisementXerfan added: “Sleep and the thyroid are linked to fundamental mechanisms of homeostasis. “There’s a complex interaction between the two systems, and sleep disturbances can influence hormonal regulation just as thyroid dysfunction can affect sleep quality.”