Interaction Between Psychotropic Drugs and Thyroid Hormone Metabolism an Overview

Abstract

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.

Inhibitions of thyroidal and extra-thyroidal T3, T4 and thyroperoxidase profiles with elevations of TSH following lithium treatment in adult and aged rats

“…It is known that lithium influences synthesis and/or metabolism of thyroid hormones at different sites. Ramschak-Schwarzer et al (37) have also noted inhibitions of T 3 and T 4 levels in the liver and kidney following extremely high doses of lithium feeding in rats. In the current study, lithium decreased liver and kidney T 3 and T 4 levels in acute (10 days) and chronic (25 days) treatments both in adult and aged rats.…”

Thyroid Function Testing

“…The cause of these changes may be secondary to decreased synthesis of thyroid hormone or modulation of deiodinase enzymes. 311,312 In vitro studies and in vivo animal studies demonstrated that chlorpromazine induced a decrease in RAIU. 313,314 However, in humans, an increase in RAIU and a decrease in renal clearance of iodide were observed after 6 weeks of treatment with chlorpromazine and procyclidine.…”

Adverse Endocrine and Metabolic Effects of Psychotropic Drugs

“…In about 10% of patients maintained on lithium, output of triiodothyronine (T3) and thyroxine (T4) is impaired, owing in part to decreased end-organ sensitivity to TSH, possibly decreased thyroid uptake of iodine, less efficient release of synthesized T3 and T4 and their decreased coupling with thyroglobulin. [95,96] Some antidepressants, anticonvulsants and antipsychotics may also decrease thyroid function. [96][97][98][99][100][101] Other agents employed for mood-stabilizing effects, including carbamazepine, divalproex sodium and lamotrigine, are far less likely to affect thyroid functioning than lithium.…”

“…[95,96] Some antidepressants, anticonvulsants and antipsychotics may also decrease thyroid function. [96][97][98][99][100][101] Other agents employed for mood-stabilizing effects, including carbamazepine, divalproex sodium and lamotrigine, are far less likely to affect thyroid functioning than lithium. [99] However, carbamazepine and phenytoin can reduce binding to thyroidbinding globulin to increase circulating levels of free thyroid hormone, as well as increasing metabolic clearance of T4.…”