Letter: T.R.H. in depression

Effects of hypothalamic peptides on the aging brain

The hypothalamic peptide hormones, TRH, LHRH (GnRH), CRH, GHRH, and GHIRH (somatostatin), influence the release of the anterior pituitary hormones, which in turn promote the release of target endocrine gland hormones and other metabolites. These latter compounds feed back to the brain to help control the secretion of the hypothalamic hormones. This is a dynamic interaction that is influenced by the aging process: Most of these hormones systems become less responsive with advancing age, due to decreased function of peptide-containing secretory neurons, a loss of hormone receptor sensitivity, and/or a reduction in the output of the target endocrine glands. That the hypothalamic peptides themselves can influence brain function is supported by the fact that most are found in areas of the brain other than the hypothalamus and that receptors for them exist in these other areas. For example, CRH is contained in a number of central neural systems that can influence behavior, including limbic areas, the hypothalamus, locus coeruleus, median raphé nuclei, and cortical interneurons. CRH has been shown to be anxiogenic in animal models, and its effect can be blocked by CRH receptor antagonists. CRH content in the locus coeruleus is particularly increased by stress and may influence norepinephrine neurotransmitter function in this structure. In aging there is a gradual reduction of the sensitivity of the brain to the negative feedback of corticosteroids, such that CRH secretion becomes somewhat increased under basal conditions. The behavioral effects of this change are unclear, however, as is the influence of stress-related activation of CRH, ACTH, and glucocorticoid secretion on behavior in the elderly. Other hypothalamic peptides have different patterns of change with aging, and some are markedly altered in pathological conditions; for example, in Alzheimer's disease the content of CRH and somatostatin in certain brain areas is decreased. However, whether the changes in hypothalamic peptides precede or follow the pathological behavioral changes, and how they participate in the changes, is still unclear.

Thyroid hormones in the treatment of affective disorders

The experience of using thyroid hormones in affective disorders is summarized. This includes: 1) Using thyroid hormones alone in depression; 2) their combined use with tricyclic antidepressants; 3) addition of thyroid hormones to nontricyclic antidepressants; 4) the use of thyroid stimulating hormone; and 5) thyrotropin releasing hormone in depression. Suggested mechanisms of action are discussed. A special attention is paid to the place of thyroid hormones in the treatment of rapid cycling affective disorder.

Treatment of endogenous depressions with thyrotropin-releasing hormone (TRH) under oral administration

In a double-blind study among six patients suffering from endogenous depression, three patients received thyrotropin-Releasing Hormone (TRH) administered orally in doses of 20 mg three times a day for 3 weeks. In an open controlled study of three patients suffering from endogenous depression, two patients received oral TRH 20 mg four times a day for 2 weeks. Degree of depression according to Hamilton's Rating Scale measured during the study showed that TRH had no antidepressant effect. Thyroxine concentration in serum (T4) increased during the period of TRH treatment.

Antagonism of isolation-induced aggression in mice by thyrotropin-relasing hormone (TRH)

TRH was shown to be an extremely potent (ED50 = 0.04 mg/kg, IP) antagonist of isolation-induced aggression in male mice. The antifighting activity of TRH was selective in that it did not produce concurrent neurological impairment or significant alterations in spontaneous locomotor activity at antiaggressive doses. This activity of TRH appeared to be a direct affect on CNS structures since neither triiodothyronine nor any of the constituent amino acids of TRH antagonized aggression in isolated mice. The results are discussed in terms of the recent clinical effectiveness of TRH in some cases of mental illness (e.g., depression and schizophrenia).

Thyrotropin-releasing hormone: differential antidepressant and endocrinological effects

In a double-blind study, three depressed subjects received thyrotropin-releasing hormone (TRH) on three successive days, and one subject similarly received placebo; all subjects were then given ECT. Two of the patients given TRH responded to ECT. One patient's reaction is of special significance because of her response to ECT, diminished thyroid-stimulating hormone response to TRH, increased growth hormone and prolactin response to stress, and antidepressant effect of TRH. These findings raise the possibility that previous conflicting reports about TRH's antidepressant effects stem from the combined study of endocrinologically distinct depressive subgroups and strongly suggest that there may be a specific subgroup that is responsive to TRH.

Thyrotropin releasing hormone (TRH) as a possible quick-acting but short-lasting antidepressant

In a double reversal design the potency of thyrotropin releasing hormone (TRH) (500 mug intravenously) as a quick-acting antidepressive agent was evaluated. A first injection did seem to give rise to a very slight short-lasting effect, though this could not be ascertained clearly. There were no visible effects after a second injection. The thyroid stimulating hormone (TSH) response curve after TRH administration in the depressive patients group was blunted in comparison with that in a matched control group of normals.