156 Chapter 5 In physiological conditions, regulation of food intake and weight homeostasis is regulated by leptin (Figure 1).12-14 Leptin is an adipokine that is mainly produced by adipose tissue, and circulating leptin concentrations are highly correlated with the amount of fat mass. It is known that in obese individuals hyperleptinemia occurs without an adequate response that reduces these high levels of leptin, suggesting a state of leptin resistance.14 A previous study in ALL patients showed that leptin levels increased almost twofold after four days of dexamethasone,8 similar to what was shown in healthy adults after two days of dexamethasone.15,16 It may be possible that the short-term side effects of dexamethasone are mediated through (partial) leptin resistance. Furthermore, sleep deprivation is known to decrease leptin levels and increase hunger and appetite,17 and leptin is associated with cancer-related fatigue in adults.18 However, the associations between dexamethasoneinduced side effects and leptin remain unclear. Therefore, the aims of the current study were to determine the influence of a five-day dexamethasone course on changes in leptin, as well as fat mass, hunger, sleep and fatigue and to assess correlations between these changes. Furthermore, we aimed to explore contributing factors to high leptin levels before and during a dexamethasone course.
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