Mesial temporal lobe epilepsy has been associated with abnormalities of reproductive physiology, but the mechanisms of hormonal dysregulation are not clear. Chronic effects of the epileptic state and the acute impact of seizures could alter hypothalamic function, which is represented by the downstream pulsatile secretion of luteinizing hormone. This study evaluates the interictal and postictal secretion of luteinizing hormone in mesial temporal lobe epilepsy. We characterized luteinizing hormone secretion in patients with mesial temporal lobe epilepsy during two 24-hour epochs: an interictal baseline and a postictal interval initiated by an electrographically confirmed spontaneous seizure. Males, rather than females, were studied so that menstrual cycles could not account for differences between epochs. Blood luteinizing hormone and prolactin (as a positive control) were measured every 10 minutes. Deconvolution analysis defined luteinizing hormone secretion in terms of interpulse interval, amplitude, and mass. Approximate entropy quantitated relative degradation in the orderliness of serial luteinizing hormone release. Interictal baseline epochs were compared to those of healthy controls with unpaired Student's t tests and between interictal and postictal epochs within epileptic patients with paired t tests. Ten epileptic men completed both interictal and postictal epochs. Interictally, seizure patients had lower mean concentrations, slower pulse rates, and higher peak amplitudes than healthy male controls. Within epileptic patients, mean interpulse interval, pulse amplitude, and pulse mass were not affected by the occurrence of seizures, whereas the orderliness of pulse mass decreased postictally. Acute seizures induced timing irregularity in luteinizing hormone secretion, whereas chronic epilepsy was associated with changes in luteinizing hormone pulse frequency, amplitude, and mass. Altered timing and regularity of neuroendocrine pulse patterns may underlie other disorders of homeostasis in mesial temporal lobe epilepsy.