Endocrine and metabolic aspects of obstructive sleep apnea sindrome: beyond obesity

Obesity is associated with multiple alterations of the endocrine systems, including abnormal circulating hormone concentrations, due to changes in their secretion pattern and/or metabolism, altered hormone transport, and/or action at the level of target tissues. Some of the endocrine abnormalities are considered as causative factors for the development of obesity, whereas others are considered to be secondary effects of obesity itself and are usually restored after weight loss. Obstructive sleep apnea syndrome (OSAS) is a serious, prevalent condition that has significant mortality and morbidity when untreated. It is strongly associated with obesity and is characterized by several endocrine and metabolic abnormalities, that are frequently more marked than those in obese patients without OSAS, suggesting that factors other than obesity per se have a role in this clinical condition. Sleep fragmentation, direct effects of hypoxia on central neurotransmitters, and hypercapnia could contribute to these peculiar endocrine changes. In this review we will revise the endocrine and metabolic changes associated to obesity and will stress the peculiar alterations that are linked to OSAS.