Clinical Significance
Leptin has traditionally been regarded as a link between fat mass, food intake, and energy expenditure. This link originally arose from animal research findings, but its application to describing human systems has since been challenged. In humans, many instances are seen where leptin dissociates from the strict role of communicating nutritional status between body and brain and no longer correlates with body fat levels:
- Leptin level is decreased after short-term fasting (24–72 hours), even when changes in fat mass are not observed.
- In obese patients with obstructive sleep apnea, leptin level is increased, but decreased after the administration of continuous positive airway pressure. In non-obese individuals, however, restful sleep (i.e., 8–12 hours of unbroken sleep) can increase leptin to normal levels.
- Serum level of leptin is reduced by sleep deprivation. However, a recent study showed that sleep deprivation was linked with higher levels of leptin.
- Leptin level is increased by perceived emotional stress.
- Leptin level is decreased or increased by increases in testosterone or estrogen level, respectively.
- Leptin level is chronically reduced by physical exercise training.
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