Thyrotropin and prolactin responses to protirelin (TRH) prior to and during chronic imipramine treatment in patients with panic disorder

Neuroendocrine predictors of the evolution of depression

Depression is both clinically and biologically a heterogeneous entity. Despite advances in psychopharmacology, a significant proportion of depressed patients either continue to have residual symptoms or do not respond to antidepressants. It has therefore become essential to determine parameters (or predictors) that would rationalize the therapeutic choice, taking into account not only the clinical features, but also the "biological state," which is a major determinant in the antidepressant response. Such predictors can derive from bioclinical correlates and, in this context, the neuroendocrine strategy appears particularly suited. Numerous studies have investigated neuroendocrine parameters--derived mainly from dynamic challenge tests--in order to (i) determine the predictive profiles of good clinical responders to given antidepressants; (ii) monitor the progression of markers in parallel with the clinical outcome; and (iii) evaluate "in vivo" in humans the mechanisms of action of antidepressant compounds (before, during, and after treatment). This article does not attempt to be exhaustive, but rather uses selected examples to illustrate the usefulness of the investigation of the adrenal and thyroid axes and the assessment of central serotonergic, noradrenergic, and dopaminergic systems by means of neuroendocrine tests. Given methodological constraints, most of these investigations--except for baseline hormone values and the dexamethasone suppression test--cannot be used routinely in psychiatry. Despite these limitations, the neuroendocrine strategy still offers new insights in biology and the treatment of depression. Its possible expansion depends mainly on the development of specific agonists or antagonists for better investigation of the receptors supposedly involved in the pathophysiology of depression. These investigations will help define more homogeneous subgroups from a bioclinical and therapeutic viewpoint.

Panic-related responses to pentagastrin, flumazenil, and thyrotropin-releasing hormone in healthy volunteers

Thyrotropin-releasing hormone ( TRH) induces some somatic symptoms that resemble those of a panic attack, without being considered to be a laboratory panicogen in panic disorder (PD) patients. This study aimed to identify doses of TRH and the laboratory panicogens, pentagastrin and flumazenil, that would produce a similar intensity of panic-related somatic symptoms in healthy volunteers because comparison of the effects of these doses in PD patients could be used to test the hypothesis that these agents have specific panicogenic effects that are not explained solely by cognitively mediated reactions to somatic symptoms. Nine subjects were administered pentagastrin (0.2 micro g/kg) and TRH (600 or 1,200 micro g) in a double-blind, randomized order, within-subjects design. Fifteen subjects received pentagastrin (0.1 micro g/kg), TRH (600 or 1200 micro g) and flumazenil (2 mg) in a double-blind, randomized order within-subjects design. Although low dose pentagastrin (0.1 micro g/kg) induced comparable cardiorespiratory responses to those of TRH, it induced greater anxiety, suggesting that TRH would not be a credible comparator for pentagastrin in challenge studies in PD. However, TRH produced equal or greater symptom and physiological responses compared with flumazenil, suggesting that flumazenil may act as a panicogen in PD via a GABAergic mechanism rather than via a cognitively mediated response to somatic symptoms. This now requires confirmation in PD patients.