Interactions exist between progestins and the gamma-aminobutyric acid (GABA) receptor subtype A where C(21)-steroids function as activators. Other interactions between progesterone and neurotransmitter systems include stimulation of dopamine release in striatal tissue, stimulation of GnRH release from hypothalamic neurons and inhibition of opioid receptor binding and activation. Cyproterone acetate increases dopaminergic responses and binds to opiate receptors independently of its classical effect on the androgen receptor. Progesterone substitution in perimenopausal women promotes length and quality of sleep. This effect seems most prominent for progesterone administered vaginally. Progestins also play a role in the pathogenesis of migraine. Migraine symptoms occur predominantly during the perimenstrual stage. Women who suffer from menstrual migraine triggered by premenstrual progesterone loss often benefit from cyclic progesterone administration. This may be because progesterone and allopregnenolone reduce meningeal release of substance P and inhibit the development of neurogenic oedema. Women whose migraine symptoms subside during pregnancy, however, benefit from intramuscular medroxyprogesterone acetate. Progesterone, generated from pregnenolone by Schwann cells, also enhances myelin synthesis. Myelination of axons is promoted when progesterone is added to cultures of rat dorsal root ganglia. No reliable data exist with respect to the effects of other progestins on demyelinating disease. Progestins promote the growth of meningioma as progesterone receptors predominate in meningioma tissue. Progesterone and synthetic progestins should therefore not be prescribed in these patients.