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Nocturnal secretion of growth hormone is impaired in patients with obstructive sleep apnea (OSA), but the metabolic consequences have not been reported. We measured blood levels of the hormones insulin, C-peptide, growth hormone, cortisol and glucagon together with the intermediary metabolites of carbohydrate (glucose, pyruvate, lactate, alanine) and lipid metabolism glycerol, nonesterified fatty acids (NEFA), 3-hydroxybutyrate in six obese nondiabetic men with OSA on two nights. In the first study, the untreated subjects showed frequent apneas and consequent hypoxemia. The hormone and metabolite concentrations were compared with those obtained on the following night when the subjects were treated effectively with nasal continuous positive airway pressure (CPAP). There were no significant differences in the concentrations of insulin, C-peptide, cortisol or glucagon. We confirmed a marked reduction in growth hormone concentrations in OSA, with a significant increase on the CPAP night. The nocturnal profiles of glucose, pyruvate, lactate, alanine and glycerol showed no differences between the two nights, but concentrations of NEFA and 3-hydroxybutyrate, both products of lipolysis, were significantly greater on the treatment night. Because growth hormone has a lipolytic action, the results suggest that suppression of secretion of growth hormone in untreated OSA results in impaired lipolysis, which is rapidly reversed by nasal CPAP.
Cooper et al. (Sat,) studied this question.