[Thyroid hormones and depressive disorders--clinical overview and perspectives. Part 2: Thyroid hormones and the central nervous system--basic research].

This paper briefly reviews present knowledge on the uptake, distribution, metabolization, and functions of thyroid hormones in the central nervous system. So far, multiple isolated effects of these hormones could be shown; e.g. a modulation of noradrenergic, serotonergic, and dopaminergic receptor function, and an influence on second messenger, calcium homeostasis, axonal transport mechanisms, and morphology. All these effects are, however, highly specific with respect to brain area and both the biochemical mechanisms and the physiological importance are poorly understood. Antidepressants and neuroleptics influence thyroid hormone metabolism in the CNS. The respective effects depend on the area under investigation, the circadian rhythm, and the specific drug. Future research should investigate primarily the biochemical mechanisms of thyroid hormone action on the central nervous system. Furthermore, it seems worthwhile to examine whether or not the different effects of psychopharmacological drugs on CNS thyroid hormone metabolism are involved in their mechanisms of action.