The effects of desipramine (DMI) and electroconvulsive shock (ECS) on the function of the hypothalamo-pituitary-thyroid axis in the rat

Effects of treatment with haloperidol and clozapine on the plasma concentrations of thyroid hormones in rats

OBJECTIVES

Psychoactive drugs are group of compounds used to treat severe mental problems, including psychosis, as well as other conditions. This study assessed clinically relevant side effects of haloperidol and clozapine on the thyroid hormones.

METHODS

Haloperidol (0.05 and 2 mg/kg) or clozapine (0.5 and 20 mg/kg) was intraperitoneally injected to male Wistar rats for 28 days. The control group received 2 ml of physiological saline. A chemiluminescent immunoassay was used to measure the plasma levels of thyroid hormones.

RESULTS

Plasma concentrations of thyroxine (T4) in rats treated with high-dose (2 mg/kg) of haloperidol decreased significantly compared to the control group (p=0.001). However, both low (0.5 mg/kg) and high clozapine (20 mg/kg) doses did not have a significant effect on the plasma concentrations of T4 and triiodothyronine (T3) (p>0.05). Neither of the compound had a significant effect on T3 plasma concentration levels (p>0.05).

CONCLUSIONS

Haloperidol and clozapine act via different mechanisms and may have dissociable effects on thyroid hormones. Following treatment with haloperidol, significant changes in T4, but not in T3, serum levels were observed. Haloperidol and clozapine had different effects on the thyroid hormone levels. These results indicate that antipsychotic treatment can contribute to the thyroid dysfunction. Therefore, greater caution should be applied to the antipsychotics use. The thyroid function of the patients should be closely monitored, while using these drugs.

Chronobiological hypothalamic-pituitary-thyroid axis status and antidepressant outcome in major depression

BACKGROUND

We previously demonstrated that the difference between 2300h and 0800h TSH response to protirelin (TRH) tests on the same day (ΔΔTSH test) is an improved measure in detecting hypothalamic-pituitary-thyroid (HPT) axis dysregulation in depression. This chronobiological index (1) is reduced in about three quarters of major depressed inpatients, and (2) is normalized after successful antidepressant treatment. In the present study, we examined whether early changes in HPT axis activity during the first 2 weeks of antidepressant treatment could be associated with subsequent outcome.

METHODS

The ΔΔTSH test was performed in 50 drug-free DSM-IV euthyroid major depressed inpatients and 50 hospitalized controls. After 2 weeks of antidepressant treatment the ΔΔTSH test was repeated in all inpatients. Antidepressant response was evaluated after 6 weeks of treatment.

RESULTS

At baseline, ΔΔTSH values were significantly lower in patients compared to controls and 38 patients (76%) showed reduced ΔΔTSH values (i.e., <2.5mU/L). After 2 weeks of antidepressant treatment, 20 patients showed ΔΔTSH normalization (among them 18 were subsequent remitters), while 18 patients did not normalize their ΔΔTSH (among them 15 were non-remitters) (p<0.00001). Among the 12 patients who had normal ΔΔTSH values at baseline, 8 out 9 who had still normal values after 2 weeks of treatment were remitters, while the 3 with worsening HPT axis function (i.e., reduced ΔΔTSH value after 2 weeks of treatment) were non-remitters (p<0.02). A logistic regression analysis revealed that ΔΔTSH levels after 2 weeks of treatment could predict the probability of remission (odds ratio [OR]=2.11, 95% confidence interval [CI]=1.31-3.41).

CONCLUSIONS

Our results suggest that after 2 weeks of antidepressant treatment: (1) chronobiological restoration of the HPT axis activity precedes clinical remission, and (2) alteration of the HPT axis is associated with treatment resistance.

Icariin from Epimedium brevicornum attenuates chronic mild stress-induced behavioral and neuroendocrinological alterations in male Wistar rats

Chronic mild stress (CMS) is suggested to produce abnormalities in the hypothalamic-pituitary-adrenal (HPA) axis and hypothalamus-pituitary-thyroid (HPT) axis. Therefore, compound that attenuates the neuroendocrinological alterations may have potential as antidepressant. The behavioral and neuroendocrinological effects of icariin, a major constituent of flavonoids isolated from Epimedium brevicornum, were investigated in the CMS model of depression in male Wistar rats. CMS procedure caused an anhedonic state in rats resulted in increased corticotropin-releasing factor (CRF) concentrations in dissected brain regions and serum, decreased total triiodothyronine (tT3) in serum with no significant changes in serum adrenocorticotrophic hormone (ACTH) and thyroxine (tT4). Administration of icariin reversed CMS-induced sucrose intake reduction and CRF elevation. These results suggested that icariin possessed potent antidepressant-like activities which were at least in part mediated by improving the abnormalities in the HPA axis functions. However, we did not find a clear correlation between the HPT axis and icariin treatment in the CMS-treated rats.

Neuroendocrine predictors of the evolution of depression

Depression is both clinically and biologically a heterogeneous entity. Despite advances in psychopharmacology, a significant proportion of depressed patients either continue to have residual symptoms or do not respond to antidepressants. It has therefore become essential to determine parameters (or predictors) that would rationalize the therapeutic choice, taking into account not only the clinical features, but also the "biological state," which is a major determinant in the antidepressant response. Such predictors can derive from bioclinical correlates and, in this context, the neuroendocrine strategy appears particularly suited. Numerous studies have investigated neuroendocrine parameters--derived mainly from dynamic challenge tests--in order to (i) determine the predictive profiles of good clinical responders to given antidepressants; (ii) monitor the progression of markers in parallel with the clinical outcome; and (iii) evaluate "in vivo" in humans the mechanisms of action of antidepressant compounds (before, during, and after treatment). This article does not attempt to be exhaustive, but rather uses selected examples to illustrate the usefulness of the investigation of the adrenal and thyroid axes and the assessment of central serotonergic, noradrenergic, and dopaminergic systems by means of neuroendocrine tests. Given methodological constraints, most of these investigations--except for baseline hormone values and the dexamethasone suppression test--cannot be used routinely in psychiatry. Despite these limitations, the neuroendocrine strategy still offers new insights in biology and the treatment of depression. Its possible expansion depends mainly on the development of specific agonists or antagonists for better investigation of the receptors supposedly involved in the pathophysiology of depression. These investigations will help define more homogeneous subgroups from a bioclinical and therapeutic viewpoint.

Thyroid accumulation and adverse effects of imipramine and desipramine in rats after long-term administration

The respective adverse effects of imipramine and desipramine on serum thyroid hormone levels and their accumulation in thyroid were investigated in male Wistar rats. Two groups of 30 rats were gavaged for 4 weeks with 30 mg/kg/day imipramine hydrochloride (IMI) or desipramine hydrochloride (DESI), while the control group (12 rats) received the arabic gum vehicle only. In the IMI-treated group, the serum thyroxine (T4) level significantly decreased (by 13%) and IMI and its metabolite DESI were accumulated in the thyroid, as pointed out by mean thyroid-to-serum concentration ratios close to 12 and 8, respectively. In the DESI-treated group, the mean thyroid-to-serum concentration ratio of the drug was close to 14, and significant decreases in both serum T4 (-20%) and triiodothyronine serum levels (-14%) were found. The accumulation of antidepressant drugs in the thyroid was more pronounced and the thyroid serum levels were even lower after DESI administration than after IMI administration. These results are in favour of an antithyroid action of IMI and DESI due to the formation of a complex in the thyroid between molecular iodine and the drugs or metabolites.

Relationship between psychotropic drugs and thyroid function: a review

Some widely used psychoactive drugs, such as tricyclic antidepressants and antipsychotic phenothiazines exhibit iatrogenic effects on the thyroid. These side effects may arise from interactions at different steps of thyroid hormone biosynthesis. These drugs can induce a change in iodine capture by thyroid cells or can complex iodine, making it unavailable for thyroid hormone synthesis and thus decreasing thyroid hormone blood levels; they can also inhibit thyroid peroxidase activity and thus T3 and T4 synthesis or enhance deiodination of T4 to T3 or to Rt3 by stimulation of deiodinase activity. Moreover, tricyclic antidepressants interfere with the hypothalamic-pituitary-thyroid axis via the noradrenergic or serotonergic systems and might therefore decrease T4 or T3 blood levels, respectively. Phenothiazines can induce autoimmune hypothyroidism, as shown by an increase in the expression of the major histocompatibility complex antigen and by a production of antithyroglobulin or antithyroperoxidase antibodies. However, all these mechanisms are only speculative in humans, as they have only been demonstrated in vitro or in animal experiments. Clinically, thyroid function and affective disorders are closely linked. On one hand, the therapeutic response to antidepressants could be influenced by the thyroid status; on the other hand, the larger the thyroxin decrease induced by antidepressants, the better the therapeutic effect might be. Moreover, cotreatment with thyroid hormones and antidepressant drugs could allow either a decrease in the rate of treatment failure or a faster recovery from depression. As antipsychotic or antidepressant treatments are administered over long periods in humans, their thyroid toxic effects must be taken seriously.

Amitriptyline inhibits the G protein and K+ channel in the cloned thyroid cell line

We have reported that thyroid K+ channel is activated by extracellular application of the thyroid-stimulating hormone (TSH) using single channel recording method performed on cloned normal rat thyroid cell (FRTL-5) membrane. Treatment of dibutyryladenosine cyclic monophosphate (Bt2 cAMP) also activated the TSH-dependent K+ channel. These findings indicate that the thyroid K+ channel is activated through the TSH-adenosine cyclic monophosphate (cAMP)-protein kinase A system. We examined the effects of amitriptyline on TSH-guanosine triphosphate binding protein (G protein)-adenylate cyclase-cAMP-K+ channel system in the cloned normal rat thyroid cell line FRTL-5. Amitriptyline inhibited the cAMP production induced by TSH. Amitriptyline also inhibited the cAMP production induced by cholera toxin, indicating that amitriptyline inhibited the thyroid G protein. Amitriptyline had no effect on TSH-receptor binding and cAMP production by forskolin (adenylate cyclase stimulator). Amitriptyline inhibited the K+ channel activation by cAMP, indicating that the suppressing mechanism is not the inhibition of TSH receptor or G protein but the direct suppression of K+ channel. It was concluded that amitriptyline inhibited the thyroid G protein and K+ channel.