Thyrotropin-releasing hormone: differential antidepressant and endocrinological effects

Hormone treatment of depression

There is a well-established relationship between alterations of various hormonal systems and psychiatric disorders, both in endocrine and psychiatric patients. This has led to clinical and research studies examining the efficacy of the different hormones for treatment of depression. These data will be reviewed with particular regard to the thyroid, gonadal, pineal, and adrenal cortex hormones. The data generally provide limited, but varying evidence for the antidepressant efficacy of these hormones.

Rapid antidepressant response after nocturnal TRH administration in patients with bipolar type I and bipolar type II major depression

BACKGROUND

Thyrotropin-releasing hormone (TRH) is a tripeptide that produces endocrine and behavioral effects in animals and humans. Some studies have shown transient antidepressant activity after morning administration of TRH. We hypothesized that nocturnal administration of TRH, when the circadian sensitivity of the TRH receptor is at its peak, may result in a more robust antidepressant effect.

METHODS

Twenty patients with bipolar (BP) type I or BP type II major depressive episode (MDE) were given nocturnal intravenous TRH 500 microg (n = 10) or saline (n = 10) at midnight in a randomized, double-blind fashion. Antidepressant activity was assessed using the Hamilton Depression Rating (HAM-D), Young Mania Rating (YMR), and Profile of Mood (POMS) scales over a 48-hour period. Thyrotropin (TSH), total T4, and free T3 concentrations were measured before and after TRH administration. Data were analyzed using chi test, Fisher exact test, and repeated-measures ANOVA.

RESULTS

Sixty percent of the TRH group and 10% of the saline group showed a > or =50% reduction in baseline total HAM-D score within 24 hours (P = 0.03). HAM-D ratings fell by an average of 52% after TRH administration versus 12% after saline administration (P = 0.038). There was a modest increase in YMR scores after TRH compared with saline (P < 0.032). No manic or hypomanic episodes were observed. Antidepressant effects of TRH lasted up to 48 hours. There was no correlation between DeltaTSH, DeltaT4, or DeltaT3 measures after TRH (or saline) administration and the change in HAM-D scores.

CONCLUSIONS

Nocturnal TRH administration may produce a rapid antidepressant effect in some patients with BP I and BP II MDE.

Nocturnal TSH and prolactin secretion during sleep deprivation and prediction of antidepressant response in patients with major depression

In order to test the hypothesis that changes in the hypothalamic-pituitary axis during sleep deprivation are related to the antidepressant effects of this procedure, we measured thyroid-stimulating hormone (TSH) and prolactin levels in 32 depressed patients at 2:00 AM during a night before, during, and after total sleep deprivation (TSD). TSH levels increased significantly (p less than 0.05) during TSD, and prolactin levels decreased significantly (p less than 0.0001). When we divided the patients into responder and nonresponder groups based on a 30% reduction in the Hamilton Rating Scale, there was no difference between the two groups in their hormone levels on the baseline, TSD, or recovery nights. Changes in prolactin or TSH were not correlated with clinical improvement when the two groups were considered together or in the responder/nonresponder groups separately. Baseline values of both hormones were significantly (p less than 0.01) correlated with their respective levels during TSD and recovery sleep. These findings indicate that the relative levels of nocturnal TSH and prolactin are stable even within acutely depressed individuals and that changes in their levels are not related to the clinical response to sleep deprivation.

TRH: behavioral and endocrine effects in man

1. The tripeptide TRH exerts a spectrum of biological activities in both animals and man. Some of these activities have been extensively studied, particularly in psychiatric patients. 2. Behaviorally, TRH appears to increase the sense of well-being, motivation, relaxation, and coping capacity in both normal subjects and patients with psychiatric and neurologic disease. These effects are not disease-specific; attempts to use TRH as a treatment tool have thus been disappointing. 3. Endocrinologically, administration of TRH stimulates the response of TSH; this response has been reported to be blunted in approximately 30% of patients with major depression. However, TSH blunting is not specific for depression, it has also been observed in a variety of other psychiatric conditions. 4. The relevance of these effects for psychiatry in general, and for psychoneuroendocrinology especially, is discussed in this review.

TRH-induced prolactin release is blunted in females with endogenous unipolar major depression

Twenty-five women with unipolar primary major depressive disorder (20 endogenous, 5 nonendogenous) and 20 female control subjects were studied with the thyrotropin-releasing hormone stimulation test (TRH-ST). Prolactin (PRL) levels were measured before and after TRH administration for patients and control subjects. For patients, thyrotropin (thyroid-stimulating hormone; TSH) levels were measured from the same serum specimens as PRL levels, and the 1 mg dexamethasone suppression test (DST) was performed. Patients with endogenous depression (ED) had significantly lower maximal serum PRL levels (max PRL) following TRH, and a significantly reduced increase over basal serum PRL (delta max PRL) compared to normal controls (NC). Nonendogenous depressed (NED) patients did not differ significantly from the ED or NC groups on either of these measures. For the ED group, delta max PRL was inversely correlated with severity of depressive symptomatology. Basal PRL levels did not differentiate the depressed subgroups (ED, NED) from each other or from the NC group. Depressed patients with blunted delta max PRL values tended to have blunted delta max TSH values and vice versa. Almost all patients with blunting of either delta max PRL or delta max TSH were also DST nonsuppressors; conversely, only about half (7 of 12) of patients who were DST nonsuppressors had either blunted delta max PRL or delta max TSH. Patients with clinical diagnoses of melancholia or psychotic features were significantly more likely to have blunted delta max PRL values than patients without these diagnoses. A disturbance of central noradrenergic function could explain these findings.

Amine metabolites and neuroendocrine responses related to depression and suicide

5-Hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) were measured in the lumbar cerebrospinal fluid of 57 drug-free female patients with DSM-III diagnoses of major unipolar or bipolar depression (n = 14), schizophrenic disorder (n = 18), alcohol dependence (n = 13) and a group of other disorders (n = 12). Following lumbar punctures all patients received a dexamethasone suppression test. Fourteen patients had attempted suicide immediately before admission, 4 of them by violent methods. Severity of depression, independent of the diagnosis, was assessed in every patient on the 24-item Hamilton scale. No significant differences in means and variances of amine metabolite or postdexamethasone plasma cortisol concentrations were found among the diagnostic subgroups. Suicidal patients, and in particular those who used violent methods, tended to have lower 5-HIAA, but not HVA, in their CSF; they also more often had non-suppression of cortisol after dexamethasone. Since correlation matrices in the diagnostic subgroups were homogeneous, we calculated partial correlations for the total group: here suicide attempts but not depression, seemed to be significantly correlated with CSF 5-HIAA. Thyrotropin stimulation tests were administered to 6 patients: maximal TSH responses showed a borderline significant correlation with CSF 5-HIAA, and a significant correlation with severity of depression. Neither suicide nor postdexamethasone cortisol levels showed any relation to maximal TSH changes.

Relationship between cerebrospinal fluid amine metabolites, neuroendocrine findings and personality dimensions (Marke-Nyman scale factors) in psychiatric patients

5-Hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) were measured in the spinal fluid of 45 women hospitalized in a psychiatric department for major depression (14 cases), schizophrenia (18 cases) and alcohol dependence (13 cases). Dexamethasone suppression tests were performed following CSF examinations in all patients, and TRH stimulation tests were also made in six subjects. All biological examinations were carried out in a drug-free state. The Marke-Nyman Temperament scale was administered to all patients as soon as severe psychotic disturbances subsided and sufficient cooperation was achieved, but no later than 10 days following biological examinations. The MNT was repeated after recovery to check reliability of the test results during an episode of a psychiatric disorder. CSF amine metabolite concentrations did not differ significantly in the three patient groups; postdexamethasone average cortisol levels were above the critical level (5 micrograms/dl) in each group, the highest values being found in major depression. One of the three MNT factors was inhomogeneous among diagnostic groups (validity: low in depression and alcoholism), but the other two also differed from a healthy control population. Correlation structure between biological and psychological variables was homogeneous throughout the diagnoses and a significant inverse correlation was found only between CSF 5-HIAA and the validity factor of MNT. Maximal TSH response to TRH stimulation correlated with both solidity and stability in the MNT scale. Since MNT results proved to be stable even during an illness episode, a possible link is suggested between personality traits and central serotonin metabolism.

Thyrotropin releasing hormone potentiates the effects of imipramine on brain serotonergic system

Daily administration of thyrotropin-releasing hormone (TRH) (20 mg/kg) for 10 days in 2 equally divided doses increased 5-hydroxytryptamine and/or 5-hydroxyindoleacetic acid levels in certain brain areas. Chronic imipramine treatment (10 mg/kg) for 10 days significantly decreased the levels of brain 5-hydroxytryptamine and 5-hydroxyindoleacetic acid. When TRH was administered concurrently with imipramine (10 mg/kg), this neuropeptide significantly potentiated the effects of imipramine on lowering of endogenous levels of 5-hydroxytryptamine (striatum, hypothalamus) and 5-hydroxyindoleacetic acid (striatum, midbrain, pons-medulla). Our data provide a possible neurochemical basis for the reported potentiation of tricyclic antidepressant action by TRH.

The behavioural actions of the hypothalamic peptides: a review

Recent work has shown that the hypothalamic peptides commonly associated with the control of pituitary function have important behavioural actions of possible psychiatric significance. Thus, vasopressin, ACTH and like peptides may influence memory processes, and ACTH and MSH given intracranially induce a peculiar stretching and yawning syndrome accompanied by penile erection and ejaculation. Thyrotrophic hormone-releasing factor potentiates behavioural excitation, somatostatin is depressive, while luteinizing hormone-releasing hormone facilitates sexual behaviour and the newly identified endorphins are markedly opioid in character. These and other activities of the hypothalamic peptides are reviewed and assessed alongside the clinical information available.

Psychoendocrinological and therapeutic effects of TRH in depression

The antidepressive efficacy of TRH was investigated in 15 endogenous depressive patients in a double-blind cross-over design. The Hamilton depression scale, the AMP (PAS) system, v. Zerssen scale and thermometer scales were used. No therapeutic effect could be demonstrated. The blunted TSH-response to TRH, which has been described by other investigators, was confirmed. There was suggestive evidence of a psychoendocrinological relationship in the sense that the more severe the "somatic depressive" syndrome as calculated from the AMP system, and the more marked the diurnal variation of the endogenous type is, the lower are the basal TSH-values and the smaller the response to TRH. Thus, TRH may become a useful tool to identify subgroups of depressive patient populations.