[Thyrotropin-releasing hormone in psychiatry: marker, predictor and therapeutical tool]

In this article the up-to-date knowledge about the neuroanatomy, physiology and pathophysiology of TRH is reviewed. The dysfunction of hypothalamo-pituitary-thyroid axis is evident in depression, alcoholism and schizophrenia. The majority of depressed patients are euthyroid with elevated plasma levels of reverse T3. On the other hand, a great number of rapid cycling bipolar patients display hypothyroidism. About 25-30 percent of patients with endogenous depression show blunted TSH response after TRH administration (TRH test). In the majority of cases the abnormal TRH test was normalized during remission. There is an associated appearance of blunted TRH test and the missing suppression of cortisol after administration of dexamethasone in patients with endogenous depression. Many factors which are not in connection with mental disorders may modify the result of TRH test. After administration of TRH to patients with endogenous depression, there is also a diminished prolactin response and a paradoxical secretion of the growth hormone. The TRH test may be valid in differentiation of endogenous depression from other depressive states, prediction of pharmacotherapeutic outcome of endogenous depression and differential diagnosis of bipolar disorder and schizophrenia. The alcoholics also show blunted TSH and prolactin response after stimulation with TRH, while paranoid schizophrenics may display hyperthyroxinaemia.