Mechanism of action of ECT in major depressive disorders: a neuroendocrine interpretation

Effects of electroconvulsive therapy on the thyrotropin-releasing hormone test in patients with depression

We investigated the acute and lasting effects of electroconvulsive therapy (ECT) on the thyroid-stimulating hormone (TSH) response to thyrotropin-releasing hormone (TRH) in patients with depression. The TRH stimulation test was conducted (1) under basal conditions, after a first ECT, and at the end of a therapeutic course of 7 ECTs in 20 inpatients with depression; (2) before the initiation of antidepressant therapy and after the therapeutic response in 16 other inpatients with depression who responded to antidepressant drug treatment; and (3) in 20 healthy control subjects. Baseline TSH levels were lower in patients with depression, especially in those with more severe depression who were considered appropriate for ECT. Before the treatment, TSH response to TRH did not differ between the patients with depression and controls; however, more blunted TSH responses to TRH were observed in these patients compared with the controls. TSH response to TRH changed neither with one ECT nor throughout consecutive ECT sessions in patients with depression. Drug treatment also was found to have no impact on this response. These findings suggest that the therapeutic action of ECT in depression is not directly related to its effects on the hypothalamic-pituitary-thyroid axis. However, possible delayed effects of ECT on the HPT axis function should not be overlooked.

Effects of antidepressant treatment on thyrotropin-releasing hormone stimulation, growth hormone response to L-DOPA, and dexamethasone suppression tests in major depressive patients

Dexamethasone suppression (DST), thyroid-stimulating hormone (TSH) and prolactin (PRL) responses to thyrotropin-releasing hormone (TRH) and growth hormone (GH) response to L-DOPA tests were evaluated in 19 depressed inpatients before the commencement of the antidepressant treatment and after the clinical response to examine: (i) the functional relationships among the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-thyroid (HPT) axis and dopaminergic system in depression, (ii) any alterations in these hormonal functions with the antidepressant treatment. TSH responses to TRH showed a tendency to increase from pre- to posttreatment period, while TRH-induced PRL and L-DOPA-induced GH responses did not change with treatment in depressed patients who responded to the treatment. Females showed significantly higher TSH and PRL responses to TRH compared to males. No interconnections were found among the responses in DST, TRH stimulation test and L-DOPA-induced GH test in the patients. The results do not support the interrelations between the abnormalities in the HPT and HPA axes and central dopaminergic activity in depression.

Effects of electroconvulsive therapy on hypothalamic-pituitary-thyroid axis activity in depressed patients

In this study, the authors aimed to test the hypothesis that electroconvulsive therapy (ECT) may cause some alterations in hypothalamic-pituitary-thyroid (HPT) axis hormones and these responses may change throughout respective ECT sessions. Nineteen depressed inpatients (8 males, 11 females; mean age+/-S.D.: 44.77+/-10.59 years) considered suitable for ECT were included in the study. Each patient was exposed to 7 ECT sessions with general anaesthesia. The blood samples for measurements of thyroid-stimulating hormone (TSH), free thyroiodothyronine (fT3) and free thyroxine (fT4) were drawn before (baseline) and after propofol, immediately after ECT, and 30 and 60 min after ECT during the first and last (seventh) ECTs. In both the first and seventh ECTs, there was a significant increase in TSH levels 30 min after ECT compared to the pre-ECT values. Additionally, a significant decrease in post-ECT fT4 values compared to the baseline values was found only during the seventh ECT. No difference was detected in the TSH, fT3 and fT4 responses to ECT between males and females, and between bipolar and unipolar depressive patients. These results show that ECT may have some effects on the HPT system. However, whether there is a relationship between these neuroendocrine responses and the therapeutic effect of ECT is not clear.

ECT for the treatment of psychiatric symptoms in Basedow's disease

To treat psychiatric symptoms associated with hyperthyroidism, we administered electroconvulsive therapy (ECT) to a patient with Basedow's disease. After unsuccessful treatment with an oral antithyroid drug, neuroleptics, and mood stabilizer, the patient recovered completely after three ECTs and did not relapse in the 40-day follow-up period. Although hyperthyroidism has been considered to induce psychiatric symptoms by enhancement of the sensitivity and turnover in catecholaminergic neurotransmission, we suggest another possible mechanism, involving translational and activational regulation of functional proteins in the brain.

Physiological effects of electroconvulsive therapy and transcranial magnetic stimulation in major depression

Major depressive episodes are associated with dysregulation of various physiologic systems. Antidepressant medications alter regulation of the hormonal and sleep systems. A thorough understanding of these changes may elucidate the pathophysiologic basis of the disorder [Amsterdam et al., 1989: Psychoneuroendocrinology 14:43-62], and interventions targeted directly at these systems are being increasingly recognized as possible treatments for depression [Wong et al., 2000: Proc Natl Acad Sci USA 97:325-330; Szuba et al., 1996: Proc Am Coll Neuropsychopharmacol Ann Meet]. These physiologic systems are regulated by the major neurotransmitters implicated in the etiology of mood disorders--norepinephrine, serotonin, and dopamine. Many of the hormones of import for this article also act as neurotransmitters and thus alter cerebral activity themselves [Owens and Nemeroff, 1993: Ciba Found Symp 172:296-308; Weitzner, 1998: Psychother Psychosom 67:125-132]. Parenteral infusion of hydrocortisone [DeBattista, 2000: Am J Psychiatry 157:1334-1337] and thyrotropin-releasing hormone (TRH) [Prange et al., 1972: Lancet 2:999-1002; Marangell et al., 1997: Arch Gen Psychiatry 54:214-222; Szuba, 1996: Proc Am Coll Neuropsychopharmacol Ann Meet.] produce acute antidepressant effects. Antagonists to corticotropin-releasing hormone and repeated parenteral infusion of TRH may have antidepressant activity when given during several weeks [Wong, 2000: Proc Natl Acad Sci USA 97:325-330; Arborelius et al., 1999: J Endocrinol 160:1-12; Callahan et al., 1997: Biol Psychiatry 41:264-272]. Manipulations of the sleep system through sleep deprivation can ameliorate depression [Szuba et al., 1994: Psychiatry Res 51:283-295; see Wirz-Justice et al., 1999: Biol Psychiatry 46:445-453 for review]. Sleep deprivation has been shown in more than three dozen studies published in the last three decades to produce marked, acute antidepressant effects in the majority of depressed individuals [Wirz-Justice, et al., 1999: Biol Psychiatry 46:445-453]. Thus, examination of the effects the two nonpharmacologic treatments, electroconvulsive therapy (ECT) and transcranial magnetic stimulation (TMS), produce in these physiologic systems may help elucidate their mechanisms of action, while enhancing understanding of the neurobiology of depressive illness. We will review these physiologic changes associated with depression, the effects that manipulations of these systems can have on depressive disorders, and then describe the effects the two techniques that can stimulate the human brain in vivo, ECT and TMS, exert on these systems.

No early effects of electroconvulsive therapy on tryptophan metabolism and disposition in endogenous depression

The possibility that a single electroconvulsive therapy (ECT) could increase tryptophan (Trp) availability to the brain for 5-hydroxytryptamine (5-HT, serotonin) synthesis was examined in 10 depressed patients before and during the 1st hour following an ECT and in 4 control (minor ear, nose, and throat surgical) subjects receiving similar premedication. Trp availability to the brain, expressed as the serum Trp: competing amino acid ratio, and related aspects of Trp disposition were not significantly altered by ECT any differently than from preoperative stress and premedication. We suggest that Trp availability to the brain and, hence, cerebral 5-HT synthesis are not altered in depressed patients early after a single ECT.

TSH response to TRH and ECT

In 31 female patients diagnosed according to DSM-III-R criteria as suffering from 'functional' psychosis (e.g., major depression, schizophrenia, mania) TRH tests were administered before, during and after a course of electroconvulsive therapy (ECT) to investigate the effects of ECT on HPT (hypothalamic-pituitary-thyroid) axis as well as the predictive value of TSH response to TRH on treatment outcome. In 20 patients all three TRH tests were available; no significant changes in the mean TSH response were found over the course of ECT; however, a change towards blunted TSH response at the end of treatment was observed. The initial TSH response did not predict the treatment outcome.

Effects of ECT course on TSH and prolactin responses to TRH in depressed patients

The thyrotropin (TSH) and prolactin (PRL) responses to TRH were studied in 15 female depressed patients with melancholia (nine unipolar, six bipolar) during an electroconvulsive therapeutic course. The test was performed before initiation of treatment, 5 days after the final ECT session, and 1 month later, when the patients were on medication with heterocyclic antidepressants (HCAs). The maximal hormonal responses were not altered 5 days after the final ECT but both increased significantly 1 month later. Responders (n = 8) and non-responders (n = 7) to ECT did not differ significantly as regards changes in delta max TSH and PRL. The seven non-responders to ECT improved markedly after 1 month's treatment with HCAs. Three out of four patients with blunted TSH response (less than 5 mu IU/ml) continued to exhibit a blunted response in both post-ECT TRH tests. The rank order of magnitude of delta max TSH remained remarkably stable throughout the assessment period as shown by the highly significant correlations between the values in the three time points.

Proposals for the mechanism of action of convulsive therapy: a synthesis

The convulsive therapies have been powerful additions to somatic treatment in psychiatry and have enjoyed widespread application for the benefit of many. A number of theories have been advanced in efforts to account for therapeutic efficacy but none has been comprehensive. These theories can be distinguished by whether they posit a central therapeutic role for stimulation, inhibition, psychological effects, or mixed processes induced by treatment. After critically reviewing extant theories, we propose a model for the effects of the convulsive therapies: Convulsive therapy is essentially nonspecific; "nonphysiological" depolarizations are distinctly important for the restoration of aberrant intravesicular transmitter ratios with resultant therapeusis. We present this model as a working hypothesis that may contribute to the guidance of research in the mechanism of action of convulsive treatment and offer several testable hypotheses in this regard.