Interaction between psychotropic drugs and thyroid hormone metabolism--an overview.

Psychotropic drugs can influence synthesis and metabolism of thyroid hormones at different sites. Generally, lithium, tricyclic antidepressants and phenothiazines lead to a reduction in synthesis and/or metabolism of thyroid hormones. The induction of autoimmune thyroid disorders by lithium and phenothiazines has been proven in animal studies and possibly can also be found in humans. Antipsychotic drugs generally exert their therapeutic effects through a modulation of the monoaminergic and serotoninergic system. At the hypothalamic level, thyrotropin releasing hormone (TRH) is controlled by the monoamonergic system and by serotonin. Depending on the specific species, there is a particular and different influence on the secretion of different hypothalamic-pituitary-thyroid (HPT)-axis hormones.

Temporary increase of plasma epinephrine affects stress responses 24 h later.

The impact of temporary (24 h) implantation of epinephrine tables on catecholamine responses to handling and immobilization 24 h later was investigated in rats. Free plasma epinephrine responded with an increase to both types of stress (77% and 326%, respectively) while controls showed a weaker response to immobilization. The basal level of free plasma norepinephrine was reduced (46% vs. controls) after epinephrine pretreatment, but neither handling nor immobilization had a specific effect on this parameter. In contrast, the basal level of free plasma dopamine was increased after epinephrine pretreatment (183%); however, as with free norepinephrine, there was no specific effect of handling or immobilization. Conjugated plasma epinephrine was significantly lowered after epinephrine pretreatment (44% vs. controls). It did not respond specifically to handling or immobilization except for a stronger response after 20 min of immobilization. Conjugated norepinephrine showed no specific response, but increased nonspecifically after extended immobilization. Conjugated dopamine was lowered (30%-48%) in the E-treated group and did not respond to stress at any time. Thus, a temporary elevation of free plasma epinephrine affected, differentially, basal levels and stress responses of free and conjugated catecholamines 24 h later.