Fax +41 61 306 12 34 E-Mail karger@karger.ch www.karger.com Letter to the Editor months (p = 0.001). WG was associated with changes of ghrelin and leptin levels at 3 and 6 months. The authors concluded that STN DBS may temporarily dysregulate the hypothalamic secre- tion of NPY and ghrelin, whereas the WG may be related to an increased production of ghrelin and leptin. These observations bear remarkable similarities to our earlier study, in which we assessed anthropometric and hormonal pro- files in 27 PD patients on the day of surgery and at 2, 4, 6 and 12 months on STN DBS [5]. Our patients’ weight continuously in- creased throughout the study, with the mean body weight change with regard to baseline being +4.16 8 3.5 kg (p ! 0.001) at 6 months and +5.18 8 5.8 kg (p ! 0.001) at 12 months. Further- more, in both studies, leptin and ghrelin levels correlated with body WG, corresponding to the known roles of the adipocyte- derived leptin and the orexigenic hormone ghrelin. Curiously enough, Markaki et al. [4] do not pay much atten- tion to their own finding of markedly decreased cortisol levels following STN DBS. Nevertheless, this result is in surprisingly precise agreement with our observation, probably shedding more light on the mechanisms of WG in PD following STN DBS (ta- ble 1). At 3 months after STN DBS, Markaki et al. [4] noticed a significant decrease in blood cortisol (–23.8%, p = 0.027). In our study, cortisol levels decreased at 2 months, (–23.9%, p ! 0.002), still remaining significantly reduced compared to baseline at 12 months after DBS implantation (–22.9%, p = 0.008) [5]. These re- sults seem to indicate the involvement of hypothalamic-pituitary- adrenal axis in the mechanisms of WG after STN DBS. It can be hypothesized that STN DBS acts on adjacent nerve fibers and structures including hypothalamic nuclei, where it suppresses se- cretion of corticotropin-releasing factor with a subsequent de- crease in the production of cortisol. Since the level of corticotro- pin-releasing factor is low, its catabolic effect is mitigated; there- fore, the homeostatic balance shifts towards predominance in It has repeatedly been shown that patients with Parkinson’s disease (PD) gain body weight under treatment with deep brain stimulation of the subthalamic nucleus (STN DBS) [1–3]. How- ever, the mechanisms underlying this weight gain (WG) remain unclear. We, therefore, read with great interest the recently pub- lished article ‘The role of ghrelin, neuropeptide Y and leptin pep- tides in weight gain after deep brain stimulation for Parkinson’s disease’ by Markaki et al. [4]. The authors performed body com- position measurements and blood sampling before, and 3 and 6 months after STN DBS in 23 PD patients, looking for relations between WG and changes in blood levels of the metabolic hor- mones ghrelin, neuropeptide Y (NPY) and leptin. A significant WG (3.09 8 5 kg, mean 8 SD, p = 0.007) was observed 3 months after surgery, with no further increase at 6 months. Also the cir- culating levels of NPY increased significantly (p = 0.05) at 3 months, while the increase of ghrelin was significant only at 6 Received: April 27, 2012 Accepted: July 5, 2012 Published online: October 17, 2012 © 2012 S. Karger AG, Basel 1011–6125/12/0906–0410$38.00/0 Accessible online at: www.karger.com/sfn Stereotact Funct Neurosurg 2012;90:410–411 DOI: 10.1159/000341707 Decrease in Blood Cortisol Corresponds to Weight Gain following Deep Brain Stimulation of the Subthalamic Nucleus in Parkinson’s Disease Evžen Růžička a , Lucie Nováková a , Robert Jech a , Dušan Urgošík a, c , Filip Růžička a , Martin Haluzík b , a Department of Neurology and Centre of Clinical Neuroscience and b Department of Internal Medicine, Charles University in Prague, First Faculty of Medicine and General University Hospital in Prague, and c Department of Stereotactic and Radiation Neurosurgery, Na Homolce Hospital, Prague, Czech Republic Prof. Evžen Růžička, MD, DSc Department of Neurology, 1st Faculty of Medicine and General University Hospital Katerinska 30 CZ–128 21 Prague (Czech Republic) Tel. +420 224 965 550, E-Mail eruzi  @  lf1.cuni.cz Table 1. Blood cortisol at different time points and its percent decrease versus baseline Baseline 1 month 2 months 3 months 4 months 6 months 12 months Markaki et al. [4] Cortisol, g/dl 17.99 NA NA 13.71 NA 15.81 NA Change to baseline, % NA NA –23.8 NA –12.1 NA Novakova et al. [5] Cortisol, nmol/l 688.96 618.78 524.26 NA 521.96 579.74 531.3 Change to baseline, % –10.2 –23.9 NA –24.2 –15.9 –22.9 Bold print indicates significant changes. Conversion factor between conventional units (g/dl) and SI units (nmol/l) for cortisol = 27.59 (source: http://www.globalrph.com/conv_si.htm). NA = Data not available.