Thyroid hormone supplementation of fluoxetine in the treatment of major depression

T3 augmentation of SSRI resistant depression

PURPOSE OF STUDY

To investigate whether the addition of triiodothyronine (T3) helps relieve depressive symptoms in non-hypothyroid major depressive disorder patients who failed to respond to an adequate course of standard SSRI antidepressant treatments.

METHODS

Patients who fulfilled the DSM-IV criteria for non-psychotic major depression, able to give informed consent, and failed to show satisfactory antidepressant response after a minimum of six weeks adequate treatment were recruited. To enter the study their Hamilton Depression (17-item HAMD) score had to be 18 or more, thyroid-stimulating hormone (TSH) value within the normal range, and a normal thyrotropin releasing hormone-stimulation test (TRH-ST). All patients continued taking the same SSRI which they had been taking before they entered the study. At the completion of TRH-SH they were all started on 25 microg of T3 and the dose was increased to 50 microg within a week when tolerated; they continued the combination of T3 and the SSRI for a minimum of three weeks.

RESULTS

Twelve patients, comprising eight females and four males, entered the study. One female patient withdrew during the first week of side effects, eleven patients completed the trial. The patients ranged from 26 to 77 years of age, with the mean age for males and females being 52.3 and 45.1 years, respectively. Five patients were taking sertraline (mean dose = 130 mg/day) and 4 were taking citalopram (mean dose = 50 mg/day), two were on fluvoxamine (150 mg/day) and one patient was on 40 mg of paroxetine. The women took a mean daily dose of 40.6 microg of T3 for a mean duration of 3.75 weeks, while the men were on a mean daily dose of 43.8 mug of T3 for 3.5 weeks. T3 augmentation was associated with a statistically significant drop (p < .003) in the mean HAMD at end of the three weeks compared to baseline scores. Five patients (42%) showed >or=50% improvement on HAMD scores, with three achieving full remission (HAMD scores<or=7) at the end of the study. There were no reliable differences between responders and non-responders in baseline HAMD scores, number of previous antidepressant trials, gender or Deltamax TSH.

CONCLUSION

T3 augmentation resulted in improvement of mood scores. The responders' rate of 42% in our study is comparable to the response rates reported using T3 or lithium to augment tricyclic antidepressants or other combination strategies used to treat resistant depression. Even though one patient withdrew prematurely due to side effects, the remaining 11 patients tolerated the addition of T3 very well. With the availability of T3, a viable, safe, inexpensive and effective augmentation treatment, the recent trend of replacing T3 with other novel strategies appears unwarranted.

Effects of triiodothyronine and fluoxetine on 5-HT1A and 5-HT1B autoreceptor activity in rat brain: regional differences

The thyroid hormone triiodothyronine (T3) augments and accelerates the effects of antidepressant drugs. Although the majority of studies showing this have used tricyclics, a few studies have shown similar effects with the selective serotonin re-uptake inhibitor (SSRI) fluoxetine. In this study we investigated the effects of fluoxetine (5 mg/kg), T3 (20 microg/kg) and the combination of these drugs, each administered daily for 7 days, on serotonergic function in the rat brain, using in vivo microdialysis. Fluoxetine alone induced a trend towards desensitization of 5-HT1A autoreceptors as shown by a reduction in the effect of 8-OH-DPAT to lower 5-HT levels in frontal cortex, and desensitized 5-HT1B autoreceptors in frontal cortex. The combination of fluoxetine and T3 induced desensitization of 5-HT1B autoreceptors in hypothalamus. Since there is evidence linking hypothalamic function and depression, we suggest that this effect may partly account for the therapeutic efficacy of the combination of an SSRI and T3.

[Potentializing of tricyclics and serotoninergics by thyroid hormones in resistant depressive disorders]

In response to the increase of resistant depressive disorders and in spite of improved treatments, numerous studies were conducted in the last thirty Years aiming at assessing the pre-morbid thyroid state of depressed patients resistant to well conducted tricyclic treatments. "Minimal" thyroid abnormalities were evidenced as well as central thyroid disorders which may not be detected by peripheral-i.e plasmatic- dosages. Regarding the premorbid thyroid status, the hypothesis of subclinical hypothyroidism was considered by many Authors. It is marked by four grades including T3 and T4 decreased levels, basal TSH concentration abnormalities as well as increased TSH response to TRH stimulation, and the presence of antimicrosomal and antithyroglobulin antibodies. Although, there are different views on the existence or not of these abnormalities, we'll focus our attention on a metaanalysis including six studies. It shows in a population with a resistant depression, 52% of patients with subclinical hypothyroidism, against 8 to 17% in patients with simple depression and 5% in the overall population.Similarly, antithyroid antibody levels (group IV hypothyroidism) were significantly higher in depressed patients (9% to 20% against 7,5% in the overall population). For many Years, a central hypothyroidism was hypothesized on the basis of an exhausted T3-T4 transference mechanism and a lowered TRH hypothalamic biodisponibility.In the last Years, new data emerged on the role of transthyretin, a cerebral carrier T4 protein, whose concentration in the CSF was found significantly lower in depressed patients than in a control group, the lowest levels being observed in the most severely depressed. This decreased level of transthyretin would result in a lower central T4 biodisponibility-hence, in view of a T4-T3 desiodation insufficiency, a T3 deficit is observed. A low transthyretin level associated or not to subclinical hypothyroidism could be a factor of depressive vulnerability on one hand, of resistance to tricyclic treatment on the other one. Conversely, subclinical hypothyroidism could be a predictive factor of a good response to a potentializing strategy. The pharmacological mechanisms involved in this potentializing phenomenon are now well known: they consist in an interaction between depression, adrenergic receptors and thyroid hormones biodisponibility. The decreased norepinephrine level observed in depressive patients is associated, in case of increased thyroid hormones biodisponibility, with a higher sensitivity of adre-nergic receptors, mostly betaadrenergic. This seems to underly the recovery process. According to some Authors, the serotoninergic system might be involved in the potentialization of tricyclics by thyroid hormones. We know that in animals with hypothyroidism, the serotonin synthesis is decreased and that the administration of T3 increases the brain levels of serotonin and its 5HIA catabolite. In addition, T3 could correct the down-regulation induced by serotoninergics on beta-adrenergic receptors. On the basis of numerous studies carried out on the potentializing of tricyclics, we suggest practical modalities of treatment - which until today did not materialize in every day practice in the absence of a clear consensus based on statistically reliable data: after four to six weeks of inefficient tricyclic or serotoninergic treatment on a correct dosage testified by plasmatic dosages, it is recommended to initiate a T3 treatment on a effective posology (25 to 50 micrograms per day), which must be reached in 2 or 3 days, except in case of rare and transitory side effects (sweating, shaking, tachycardia, nervousness, anxiety). If the treatment is not rapidly efficient, it must be discontinued in case there is no improvement after 3 weeks. Until today, there is no consensus about the duration of a T3 treatment. It is important to take into account the predictive criteria of good or bad response to a T3 potentialization, since they have direct consequences on the management of depressed patients. For example, a high degree of chronic evolution with resistance to numerous treatments, associated disorders according to the DSM IV axis I and a comorbidity of addiction, point to a bad prognosis of a potentialization treatment. In addition, we'll examine the few recent studies on the potentializing of serotoninergic antidepressant drugs by thyroid hormones.

Risk of adverse events with the use of augmentation therapy for the treatment of resistant depression

Augmentation therapy is used for those situations where a patient's depression is either treatment-resistant, or partially and/or insufficiently responsive to treatment. It also may be used to attempt to induce a more rapid treatment response. Using drugs together may increase the risk of adverse effects, through potentiation of existing adverse effects or alterations in plasma concentrations of the drug. It is important that clinicians are aware of potential risks of augmentation therapy. Lithium augmentation of a tricyclic antidepressant is relatively well tolerated and the dangers are no greater than using these medications on their own. There are also no reports of serious adverse events when lithium is added to a monoamine oxidase inhibitor. With lithium augmentation of selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitor (SSRI) therapy there have been case reports of the development of a central serotonin syndrome, and thus caution must exercised. A serious concern when using a tricyclic antidepressant to augment an SSRI is the effect of the SSRI on the cytochrome P450 system and the resulting significant increase in tricyclic antidepressant blood concentrations. Augmentation with thyroid hormones appears to be well tolerated and effective. Case reports and open studies indicate that augmentation with buspirone and the psychostimulants, carbamazepine and valproic acid (valproate sodium) is effective and results in minimal adverse effects. However, there is no empirical evidence supporting these results. Recent work supports the tolerability and efficacy of pindolol augmentation. Considerable caution should be exercised when combining psychotropic drugs. The practitioner should only do so with a full knowledge of the compounds involved and their pharmacological properties.

The thyroid axis and depression

Hypothyroidism may give rise to frank depression that usually responds to thyroxine therapy. Depressed subjects with subclinical hypothyroidism and/or autoimmune thyroiditis should probably also be treated similarly. Most patients with depression, although generally viewed as chemically euthyroid, have alterations in their thyroid function including slight elevation of the serum thyroxine (T4), blunted thyrotropin (TSH) response to thyrotropin-releasing hormone (TRH) stimulation, and loss of the nocturnal TSH rise. These changes are generally reversed following alleviation of the depression. The role of adjuvant triiodothyronine (T3) treatment in resistant depression has not been established, but the data suggest that it will be beneficial in about 25% of cases. However, controlled trials to establish this approach are needed. The underlying mechanism leading to the beneficial response from T3 is unknown, but may reflect brain hypothyroidism in the context of systemic euthyroidism. The hypothalamus in culture, which is analogous to a deafferentated hypothalamus in vivo, shows a paradoxic increase in TRH production after glucocorticoid stimulation. It is known that in human depression there is a functional disconnection of the hypothalamus with impairment of the inhibitory glucocorticoid feedback pathway from the hippocampus to the hypothalamus that results in the typical elevated cortisol levels and impaired dexamethasone suppression. It is postulated that a similar situation prevails with regards to the thyroid axis and that the increased T4 in depression, as well as the blunted TSH response to exogenous TRH, reflects glucocorticoid activation of the TRH neuron leading to increased TRH secretion with resultant down regulation of the TRH receptor on the thyrotrope. Normalization of thyroid function after treatment may result in part from an inhibitory response of the TRH neuron to antidepressant medication, although other effects may also be responsible.

A review of the use of augmentation therapy for the treatment of resistant depression: implications for the clinician

OBJECTIVE

To critically review the literature on augmentation therapy in resistant depression in order to assist the clinician to make a reasoned choice. Augmentation therapy is defined as the addition of a second agent to an existing antidepressant regimen with the aim of achieving improved clinical response.

METHOD

The available literature which related specifically to currently popular augmentation strategies in treatment resistant depression for the past 20 years was examined. The scientific evidence supporting the efficacy of these regimens and their safety was reviewed.

RESULTS

Considerable research on lithium augmentation has been undertaken, and on triiodothyronine augmentation to a lesser degree. A number of other drugs have been trialed as augmentation agents with claims of success; however, most of the evidence supporting these agents is anecdotal and in the form of case reports. There are very few well-performed double-blind placebo-controlled studies of augmentation therapy.

CONCLUSIONS

Because of possible complex pharmacodynamic and pharmacokinetic interactions, augmentation therapy is not without its potential complications. Lithium augmentation of tricyclic antidepressants can be recommended as a safe and effective strategy and there is a body of scientific evidence supporting the addition of T3 as an effective augmentation agent. Recent research with pindolol augmentation of selective serotonin re-uptake inhibitors (SSRIs) is encouraging, but these findings require replication. There is no empirical evidence supporting buspirone, carbamazepine, sodium valproate, methylphenidate or amphetamine as effective augmentation agents, or that adding a tricyclic to a SSRI has usefulness in relieving depressive symptoms. There is a need for considerable research in this area, with more prospective well-controlled placebo studies.

Does thyroid hormone have a role as adjunctive therapy in depression?

Depression is associated with abnormalities of the thyroid axis, but the role of thyroid hormone therapy is controversial. In patients presenting with depression, the thyroid status should be carefully evaluated since hypothyroidism can cause depression. Frank hypothyroidism should be treated in the usual fashion with L-thyroxine, which may reverse the depressive state. If subclinical hypothyroidism and/or autoimmune thyroiditis are present, T3 adjuvant administration (25 micrograms/day) should be seriously considered in patients resistant to tricyclic antidepressant (TCA) (and probably also) serotonin selective reuptake inhibitor (SSRI) medication. The possible efficacy of adjuvant T4 in reversing the depression of such subjects appears less than T3. In depressed patients with TCA or SSRI resistance and no evidence of hypothyroidism, the data available do not establish the therapeutic role of T3 in this situation. Multicenter controlled studies of T3 adjuvant therapy are required. The possible mechanisms through which T3 adjuvant therapy might be efficacious are discussed.