Exaggerated TSH responses to TRH in depressed patients with "normal" baseline TSH

BACKGROUND

Subclinical hypothyroidism (elevated thyroid-stimulating hormone [TSH] with normal thyroid hormone levels) can present with depression. This may be confirmed by an exaggerated TSH response to thyrotropin-releasing hormone (TRH) on the TRH stimulation test (TRH-ST). The objective of this study was to determine the prevalence of exaggerated TRH-ST results in a sample of depressed patients with "high-normal" screening TSH levels.

METHOD

Depressed patients with TSH levels of 3.00-5.50 mIU/L underwent a TRH-ST. After baseline TSH was drawn, TRH 400 micrograms was injected intravenously, and TSH samples were drawn at +20 min, +30 min, and +40 min postinjection. A rise in TSH after TRH (peak value minus baseline) of > 25 mIU/L represented an exaggerated TSH response.

RESULTS

Twenty-three (38%) of 60 patients had an exaggerated TSH response to TRH. The 38% prevalence is significantly (Chi 2 = 59.65, df = 1, p < .001) greater than the 6% prevalence of positive TRH-ST results reported in the euthyroid general population. The prevalence of positive TRH-ST results was not attributable to differential patterns of psychotropic or thyroid hormone treatment. Unexpected observations were a lack of correlation in TSH levels week to week (r = .17, N.S.) and a lack of correlation between screening TSH value and subsequent TRH-ST results (r = .28, N.S.).

CONCLUSION

Subtle thyroid underfunction may be contributing to depression in some patients with TSH in the upper half of the range usually considered normal. If so, then the TRH-ST may be more sensitive in identifying this than measurement of TSH alone.

AIDS-related obsessive compulsive disorder: deconditioning based on fluoxetine-induced inhibition of anxiety

Abel's (1993) review of treatments for obsessive compulsive disorder (OCD) indicated that both behavioral treatment (exposure with response prevention, and biological treatment (specific serotonin reuptake inhibiting drugs) are effective. It was recognized that having both available for patients is preferable because there would be situations where one treatment is more appropriate than the other. One indication for using drugs would be where situational constraints do not allow for effective exposure treatment. We present a case study of a microbiology technician with AIDS-related OCD who had an excellent response to the administration of fluoxetine without relapse when the drug was discontinued.

Managing rapid metabolizers of antidepressants

Depressed patients who rapidly metabolize antidepressants may be common, and may not respond to even high doses of antidepressants if subtherapeutic plasma levels are produced. Rapid metabolizers (RMs) are identifiable if patients are on tricyclic antidepressants (TCAs), and TCA plasma levels (commonly available) are monitored. Strategies to achieve therapeutic levels in RMs include: (1) megaprescribing, or (2) inhibiting the metabolism of the parent drug. Megaprescribing TCAs runs the risk of markedly elevating levels of potentially toxic hydroxy metabolites. In this study twelve depressed, non-responding RMs were identified while taking the TCA, desipramine. Fluoxetine or paroxetine, selective serotonin re-uptake inhibitors (SSRIs) known to potently inhibit cytochrome P450 2D6 (the isoenzyme responsible for desipramine metabolism), was then added to continuing desipramine. Therapeutic range desipramine levels were achieved in ten patients, and seven of the ten achieved excellent or good sustained responses. The combination SSRI and TCA therapy was well tolerated. Whether response primarily reflected the TCA at therapeutic range levels, or a synergistic serotonin-noradrenaline interaction between the respective antidepressants, requires further clarification. The results of this open study suggest the need for controlled trials of antidepressant metabolism inhibition in RMs.

Rapid cycling triggered by pindolol augmentation of paroxetine, but not with desipramine

A treatment-resistant depressed patient developed bipolar rapid cycling in response to pindolol augmentation of paroxetine, after failing to respond in any fashion to pindolol added to desipramine. The rapid cycling initially faded, but recurred after the pindolol dose was increased (in combination with paroxetine) in an attempt to treat a relapse into depression. Her differential development of rapid cycling with pindolol in combination with the SSRI is in keeping with the theory that pindolol augmentation operates via a serotonergic mechanism.

Drugs and the DST: need for a reappraisal

It has generally been assumed that psychotropic drugs do not influence results on the dexamethasone suppression test (DST), except in some specific situations. Yet they directly affect the activity of many neurotransmitter systems, which in turn regulate hypothalamic-pituitary-adrenal (HPA) axis functioning. Several reports have shown correlations between the intake of or recent withdrawal from psychoactive substances and changes in DST results. A review of the DST literature reveals that these effects have not been controlled in most DST studies. It is therefore possible that the consequences of intake of psychotropic agents may have contributed to the debate surrounding the DST by producing unappreciated spurious DST results.

Methylene blue: a reliable and practical marker for validating compliance on the DST

Assurance of compliance (ingestion of dexamethasone) is crucial for interpreting plasma cortisol results on the DST. In this double-blind study of 13 subjects, methylene blue (MB) 50 mg was combined with dexamethasone 1 mg in single capsules, and the resulting blue-green urinary color after ingestion was found to reliably validate compliance in 100% of patients and controls. The addition of MB did not influence DST results (i.e., plasma cortisol, plasma dexamethasone). Adding MB to dexamethasone as a marker is a reliable and safe means of validating compliance on the DST and is considerably more practical than plasma dexamethasone level determinations.

Psychotropic drug withdrawal and the dexamethasone suppression test

In a prospective study of 25 patients from the time of hospitalization, seven had recently discontinued psychotropic agents (including antidepressants, neuroleptics, and benzodiazepines). All seven had positive dexamethasone suppression test results after 1 week of hospitalization. This phenomenon did not occur in any of the other subjects who had not discontinued such medications. Some of the subjects with postdexamethasone cortisol increases reported drug discontinuation in the drug histories they gave at admission, but in three, drug screening provided the only evidence of prior drug use. Medication withdrawal may be an underappreciated confounding variable in DST studies.

Dexamethasone suppression test results in delusional versus nondelusional depression: preliminary evidence of distinct clinical entities

Two patients with major affective disorder--one unipolar and one bipolar--exhibited normal DSTs while psychotically depressed (mood congruent delusions), yet exhibited nonsuppression on the DST in the course of subsequent separate nonpsychotic depressive episodes. If valid, these results may provide further evidence for considering psychotic and nonpsychotic depression as clinically distinct entities.

Massive eosinophilic reaction to desipramine in conjunction with pneumonia

The authors report on a female patient with bipolar affective disorder who presented with marked eosinophilia in conjunction with pneumonia five days after a medication change from amitriptyline to desipramine (for intolerable dry mouth). She improved with discontinuance of medications and supportive management, and her eosinophilia normalized. Reinstitution of desipramine was followed by prompt appearance of asymptomatic eosinophilia, which resolved with discontinuation of desipramine. A subsequent depression managed with amitriptyline was followed by no abnormal white blood count findings. Eosinophilia is occasionally encountered in imipramine or desipramine therapy and, although usually asymptomatic, appears to be manageable by switching to amitriptyline or nortriptyline.