AMPLITUDE-MEDIATED CIRCADIAN VARIATIONS IN LH PULSATILE SECRETION OF LH ARE ATTENUATED IN MESIAL TEMPORAL LOBE EPILEPSY
Abstract number :
1.122
Submission category :
Year :
2003
Submission ID :
4032
Source :
www.aesnet.org
Presentation date :
12/6/2003 12:00:00 AM
Published date :
Dec 1, 2003, 06:00 AM
Authors :
Mark Quigg, Martin Straume, Johannes D. Veldhuis Department of Neurology, University of Virginia, Charlottesville, VA; Department of Internal Medicine, Division of Endocrinology, University of Virginia, Charlottesville, VA
Mesial temporal lobe epilepsy (MTLE) is associated with abnormalities in reproductive physiology, but the mechanisms of hormonal dysregulation are not clear. Hypothalamic regulation of the reproductive axis, represented by the downstream pulsatile secretion of luteinizing hormone, (LH) has been shown to be altered interictally and postictally in MTLE. Animal data suggests that LH has a circadian organization. This study was performed to determine if LH in humans has diurnally-mediated patterns of secretion that may be altered by the epileptic state.
We characterized LH secretion in 10 patients with MTLE during two 24 hour epochs: a interictal baseline, and a postictal interval initiated by an electrographically confirmed spontaneous seizure. Males, rather than females, were used to insure that menstrual cycles could not account for differences between epochs. Serum LH was measured every 10 minutes. Deconvolution analysis defined hormone secretion in terms of pulse rate and amplitude. Pulses were grouped together into 4 time-of-day phase groups: (I) 0101-0700, (II) 0701-1300, (III) 1301-1900, (IV) 1900-0100. Data were compared to that from 10 healthy controls. Distributions of pulse rate and amplitude among phases were tested with ANOVA.
Pulse rates tended to differ among circadian phases in controls (P=0.05) with the slowest pulse rate during phase I, but did not differ significantly among phases in either baseline or postictal epochs in patients with MTLE (baseline P=0.30, postictal P=0.68). Pulse amplitudes differed significantly by phase among controls, with the largest amplitudes during phase I and the smallest at phase III (P[lt]0.0001). No differences among phases were present among baseline or postictal epochs in MTLE (baseline P=0.58, postictal P=0.24). Peak amplitudes at baseline epochs in MTLE tended to occur during phase II and nadirs in phase IV, suggesting a diurnal shift in pulse amplitude.
This study demonstrated that the pulsatile secretion of LH in healthy men is a diurnally-phasic pattern of secretion with the largest pulses occurring in the late night-early morning. Diurnal variations are modulated mainly by variations in pulse amplitude rather than in rate. In contrast, men with MTLE lack phasic differences in LH secretion both interictally and postictally. Altered daily patterns of neuroendocrine signals may underlie other disorders of homeostasis in MTLE.
[Supported by: NIH[ndash]M01RR008847 and NINDS K08 NS02021 ]