Wednesday, April 23, 2014

Obstructive sleep apnea and growth hormone

Growth hormone (GH) is secreted at night during our deepest levels of sleep. As the name implies, GH is involved in growth of our bodies. Too much GH as a child can result in a condition called acromegaly. The actor Richard Kiel, who played the character Jaws in two of the James Bond movies, has this condition. Too little GH can also negatively impact cardiovascular health as well as effect carbohydrate, fat, and lipid metabolism. GH is part of a group of hormones that include Insulin-like growth factor-1 (IGF-1) and IGF-1 binding proteins.

Obstructive sleep apnea (OSA) could reduce GH secretion due to the brief arousals from sleep, especially deep sleep. OSA can also affect GH levels by the repetitive oxygen level drops. It's been theorized that regular CPAP use may reverse the effects of OSA on GH. Previous studies have been inadequate to answer this question definitively. This study sought to determine if long term CPAP affects GH levels.

Researchers performed a randomized, double-blind, sham-controlled parallel group study. The participants were all men with moderate to severe OSA. They were randomized to receive either 12 weeks of real or sham CPAP. At the end of the 12 week period, all participants were put on real CPAP for another 12 weeks. The results showed that GH secretion was higher in those treated with real CPAP for 12 weeks compared to sham CPAP. Interestingly, the increase in GH was not due to improvements in the amount of deep sleep. Instead, the improvements in GH were associated with reduction in the oxygen level drops. Another interesting result was that the participants used real CPAP only 3.6 +/- 1.9 hours per night and the sham CPAP only 2.8 +/- 2.1 hours per night. Since most people sleep 7-8 hours per night, that amount of CPAP usage is low, yet the therapy still seemed to have a positive effect on GH.

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