Sleep apnea and hypothyroidism go hand in hand. Some studies even show that thyroid hormone treatment cures the obstructive sleep apnea (OSA). This is because hypothyroidism thickens the pharyngeal walls (tissue in the throat area), which narrows the upper airways. Bringing thyroid levels up sometimes reverses this thickening. Sleep apnea may persist in spite of thyroid treatment, however, if the patient suffers from skeletal defects or obesity.
In one overnight sleep study of hypothyroid patients, 25% showed mild to severe obstructive sleep apnea. The remaining 75% without OSA were younger and had a lower body weight. Interestingly, all of these hypothyroid patients were snorers. Their snoring ended only after a year of thyroid hormone replacement therapy.
Poor, unrefreshing sleep is another sign of hypothyroidism. This is because hypothyroid patients do not get enough of the deeper stage 3 and 4 levels of sleep. Insomnia and sleep apnea were discussed in a previous article: Can hypothyroidism cause insomnia?
If you’re hypothyroid, having sleep issues, and considering a CPAP (continuous positive airway pressure) machine, it would be a good idea to first evaluate whether your thyroid levels are optimal. You can be hypothyroid even with a normal TSH. A CPAP machine uses mild air pressure to keep the airways open in people who stop breathing or have shallow breathing when they sleep. In hypothyroidism, the respiratory muscles are weak due to a thyroid hormone deficiency. Raising thyroid levels normalizes breathing, which then makes a CPAP unnecessary for some people. When I used to take 1.5 grain of desiccated thyroid, I would often wake in the middle of the night gasping for air. I no longer do that now that I’ve combined a reduced dose of desiccated thyroid with levothyroxine, so that my T4 is no longer at the bottom of the reference range.
 Skjodt, Neil M., R. A. J. Atkar, and Paul A. Easton. “Screening for hypothyroidism in sleep apnea.” American journal of respiratory and critical care medicine 160.2 (1999): 732-735.
 Attal, Pierre, and Philippe Chanson. “Endocrine aspects of obstructive sleep apnea.” The Journal of Clinical Endocrinology & Metabolism 95.2 (2010): 483-495.
 Lin, C. C., K. W. Tsan, and P. J. Chen. “The relationship between sleep apnea syndrome and hypothyroidism.” CHEST Journal 102.6 (1992): 1663-1667.
 Siafakas, Nikolaos M., et al. “Respiratory muscle strength in hypothyroidism.”CHEST Journal 102.1 (1992): 189-194.