People with epilepsy have a lower seizure threshold than do others. The limbic system is the most sensitive part of the brain regarding seizures. Heather Edwards theorised that this is because the limbic system contains the highest number of sex steroid receptors. It is believed that fluctuations in the ratio of estrogen to progesterone may affect the number of seizures experienced. Estrogen lowers seizure threshold making it easier for neurons to misfire.
Progesterone raises the seizure threshold making it harder for neurons to misfire.
Heather noted that estrogen may turn on the stress axis as well as working directly on the hippocampus and amygdala, thereby increasing the brain's seizure potential through two different routes. More information about catamenial seizures may be found in the article Seizures and the Menstrual Cycle by Nancy Noldy-MacLean, describing her research, and through links to other sites .