II. The TRH Test

Abstract

Anterior pituitary response to TRH 200 micrograms i.v. was studied in ten chronic schizophrenic patients during long-term neuroleptic treatment. Nine patients had normal prolactin (PRL) response as compared with controls but in one the response was blunted; one patient had an exaggerated response. Prolactin increment was higher following TRH than haloperidol challenge. No growth hormone (GH) response to TRH was found and TSH responses were comparable to controls.

Influence of the dosing interval on prolactin release after remoxipride.

“…The peak plasma prolactin levels (Cmax,PRL) have been reported to be dose-related up to a maximal release following administration of remoxipride [13,14,29], sulpiride [16,[21][22][23][24][25] and also following TRH [26,27]. Maximal prolactin peak concentrations are expected to be achieved with the doses of remoxipride and TRH administered in the present study [26,27].…”

“…Maximal prolactin peak concentrations are expected to be achieved with the doses of remoxipride and TRH administered in the present study [26,27].…”

“…infusions of remoxipride increased rapidly within 10 min and the peak was reached at 30-60 min. A rapid rise and a short tmax of prolactin has been suggested to indicate a direct action on the receptors on the lactotrophs in the pituitary by TRH [26,27,39] and sulpiride [15,24]. NSa-e P < 0.05b, NSC-e tCalculated from the individual mean values.…”

Effects of Six Weeks’ Neuroleptic Treatment on the Pituitary-Thyroid Axis in Schizophrenic Patients

“…Similar findings in unmedicated schizophrenics have already been presented by previous authors [10,27], After the 6 weeks' neuroleptic treatment, our patients tended to have higher APRL values at 14.00 and 24.00 h, in com parison to their pretreatment values; however, this dif ference reaches statistical significance for only the APRL values at 24.00 h. These findings might be considered as suggesting that the sensitivity of the pituitary lactotrophs to stimulation with TRH at 14.00 and 24.00 h, particu larly at 24.00 h, in schizophrenic patients was increased during the 6 weeks' neuroleptic treatment. However, mention should be made of reports [11,28] according to which the PRL response to TRH in chronically (i.e., for more than 5 years) neuroleptic-treated schizophrenic patients is comparable to that of normal controls. Prob ably, the neuroleptic treatment of schizophrenic patients for more than 5 years results in the development of tol erance to the PRL-increasing effect of neuroleptics in the tuberoinfundibular system.…”