Hypothalamic-pituitary-adrenal axis dysregulation among diabetic outpatients

We compared insulin-requiring diabetic outpatients (n = 49) with normal controls (n = 42) for indices of hypothalamic-pituitary-adrenal (HPA) axis activity. Diabetic patients showed significantly elevated 9 a.m. plasma levels of cortisol as well as significantly elevated plasma levels of cortisol and adrenocorticotropic hormone (ACTH) at both 4 p.m. before and 4 p.m. after dexamethasone. Also, there was a significant correlation between postdexamethasone plasma levels of ACTH and duration of diabetes. These results suggest that HPA-axis dysregulation is found among diabetic outpatients. The possible psychiatric implications are discussed.     

Hypothalamic-pituitary-adrenal axis interaction with prostaglandins

1. The major PGE2 plasma metabolite, 15-keto-13, 14-dihydro-PGE (PGEM) was measured during metyrapone, dexamethasone and ACTH tests in order to elucidate if plasma PGE was affected by short term changes of the hypothalamic-pituitary adrenal axis function in man. 2. Plasma PGEM, serum cortisol and serum 11-deoxycortisol were determined by RIA. 3. Metyrapone (an inhibitor of adrenal 11 beta-hydroxylase), 250-1000 mg was given orally at 4 hour intervals for 20 hours. PGEM, cortisol and 11-deoxycortisol were measured before and 10 and 22 hours after the start of metyrapone in 10 patients evaluated for pituitary disease. 4. Dexamethasone, 1 mg orally, was given at 23 hours on day one and 25 IU (1-24) ACTH were given iv at 8 hours on day two. Blood was drawn for determination of PGEM and cortisol at 8 hours day one, and 8 hours day two. After the ACTH injection, blood was drawn at 90 minutes (for PGEM) and at 120 minutes (for PGEM and cortisol). 10 subjects aged 21-62 years were studied. 5. Plasma PGEM levels were significantly increased after metyrapone, concomitantly with the lowering of serum cortisol levels. 6. No difference in the PGEM increase between patients with normal or subnormal 11-deoxycortisol response was found. 7. A significant increase in plasma PGEM levels was found when serum cortisol was suppressed 9 hours after dexamethasone administration. 8. Glucocorticoids inhibit synthesis of eicosanoids and the present results suggest that short term decrease in cortisol may stimulate PG synthesis.     

Plasma ACTH levels in primary depression: relationship to the 24-hour dexamethasone suppression test

The failure of adequate cortisol suppression after 1 mg dexamethasone in 50% of patients with endogenous depression has been attributed to abnormal hypothalamic-pituitary-adrenal axis regulation, resulting in high levels of adrenocorticotropic hormone (ACTH). Because studies of plasma ACTH have been conflicting, we studied plasma ACTH levels during the 24-hour dexamethasone suppression test in a homogeneous group of 29 hospitalized patients with primary endogenous depression and 19 normal volunteers. No differences were found in ACTH levels among normal volunteers, depressed cortisol suppressors, and depressed cortisol nonsuppressors at either 4 p.m. or 11 p.m.     

Measurement of ACTH and prolactin in the dexamethasone suppression test

Plasma concentrations of ACTH and prolactin were measured in psychiatric inpatients at 8 a.m. and 4 p.m. before and after the standard 1 mg overnight Dexamethasone Suppression Test (DST). Plasma concentrations of cortisol were measured at 8 a.m. and 4 p.m., and 11 p.m. before and after 1 mg dexamethasone. Dexamethasone suppressed plasma concentrations of ACTH, prolactin and cortisol in the subject group as a whole. "Cut Points" obtained using Fisher's Exact Test identified plasma ACTH values at 8 a.m. baseline, 4 p.m. baseline and 8 a.m. post-dexamethasone and plasma prolactin values at all four times that significantly differentiated patients with bipolar depressive disorder and major depressive disorder from other psychiatric patients. There were no cut points found at any of the six times for plasma levels of cortisol that significantly differentiated between these two diagnostic groups. Of interest in this subject population, basal (pre-dexamethasone) plasma concentrations were of more diagnostic information than post-dexamethasone values. These pilot findings suggest that monitoring plasma prolactin and ACTH concentrations before and after dexamethasone might increase the sensitivity and specificity of this laboratory test for depression.     

The HPA axis response to insulin hypoglycemia in depression

Dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis, demonstrated by failure to suppress cortisol secretion after dexamethasone, is found in approximately 50% of patients with major depression (MD). In this study, we examined the response of adrenocorticotrophic hormone (ACTH) and cortisol to insulin-induced hypoglycemia in 20 healthy controls and 18 inpatients with MD [12 dexamethasone suppressors (S) and 5 dexamethasone nonsuppressors (NS)]. After the administration of 0.15 U/kg of regular insulin, both controls and patients with MD showed an increase in plasma ACTH and cortisol levels. Controls had a significantly higher ACTH peak (p less than 0.01) and ACTH increment (p less than 0.01) than MD patients. There were no statistically significant differences between patients who were S and NS. Although baseline plasma cortisol levels were significantly higher in MD patients, there were no significant differences in the peak cortisol or increment in plasma cortisol after hypoglycemia between patients with MD and controls or between patients who were S and those who were NS. These findings suggest that a defect exists in the regulation of the HPA axis at the pituitary level in MD and that this defect is not necessarily reflected in the dexamethasone suppression status of the patient.     

Metyrapone effects on beta-endorphin, ACTH and cortisol levels after chronic opiate receptor stimulation in man

The aim of this study was to evaluate beta-endorphin, ACTH, and cortisol plasma levels during metyrapone administration in man after chronic opioid receptor stimulation. Metyrapone (750 mg every 4 hr for 6 doses) was administered to ten male heroin addicts, who had been on a maintenance therapy with methadone for at least 6 months and to ten healthy sex- and age-matched volunteers. Before metyrapone administration the basal levels of cortisol and ACTH were significantly decreased in addicts as compared to normal controls, while plasma beta-endorphin was not different. The response of beta-endorphin and ACTH to metyrapone administration was significantly blunted in addicts (p less than 0.01). These results suggest that the chronic stimulation of opiate receptors can impair the function of the anterior pituitary gland.     

Pathophysiology of hypercortisolism in depression: pituitary and adrenal responses to low glucocorticoid feedback

Carroll BJ, Iranmanesh A, Keenan DM, Cassidy F, Wilson WH, Veldhuis JD. Pathophysiology of hypercortisolism in depression: pituitary and adrenal responses to low glucocorticoid feedback. Objective: To test three theories of hypercortisolemia in depression–hypothalamic overdrive, impaired glucocorticoid feedback, or autonomous cortisol production. Method: We applied an overnight low‐cortisol feedback strategy by administering metyrapone to hypercortisolemic depressed in‐patients and control subjects. Results: Under metyrapone, the increases of plasma adrenocorticotropic hormone (ACTH) concentrations and of basal and pulsatile ACTH secretion were not exaggerated in hypercortisolemic depressed patients compared with control subjects. ACTH approximate entropy (ApEn) did not differ at baseline or under metyrapone. Thus, neither hypothalamic overdrive nor irregular ACTH secretion was seen. We did not detect impaired cortisol feedback: the ACTH response was not reduced, and ApEn measures that are sensitive to feedback changes were comparable in both groups. Metyrapone disrupted cortisol secretory regularity in depressed and control subjects. On the baseline day, basal cortisol secretion was significantly increased and was highly irregular (high ApEn), and ACTH‐cortisol cross‐ApEn was markedly elevated in high‐cortisol patients. Conclusion: Classical feed‐forward overdrive and impaired feedback theories of hypercortisolemia in depression were not supported. Depressive hypercortisolemia may result from alternative pathophysiological mechanisms involving irregular basal hypersecretion of cortisol, associated with adrenal enlargement, possibly through splanchnic sympathetic activation of the adrenal cortex.     

Abnormalities at different levels of the hypothalamic-pituitary-adrenocortical axis early after stroke.

BACKGROUND AND PURPOSE: Hypercortisolism is common in stroke patients. The aim of this study was to investigate possible disturbances at different sites within the hypothalamic-pituitary-adrenal axis. We also studied possible associations between hypercortisolism and clinical manifestations of brain dysfunction. METHODS: Patients with an acute ischemic stroke (n = 16; mean +/- SD age, 71 +/- 11 years) were compared with healthy elderly subjects (n = 9). We performed a short adrenocorticotropic hormone (ACTH) test with 0.25 mg 1-24 ACTH injected intravenously and an overnight dexamethasone suppression test with 1 mg dexamethasone given orally at 11 PM. RESULTS: Serum cortisol levels after dexamethasone at 8 AM were significantly higher in stroke patients (p = 0.003). The area under the curve for the cortisol response to ACTH was elevated in seven (47%) of stroke patients, and the centered cumulative cortisol response was elevated in three (20%) patients. The area under the curve response correlated significantly to the presence of an acute confusional state and male sex in stroke patients (rs = 0.63 and rs = 0.62, respectively; p < 0.05), whereas the centered cumulative cortisol response diminished with increasing age (rs = -0.62; p < 0.05). Postdexamethasone cortisol levels were significantly correlated to the presence of an acute confusional state and to extensive limb paresis (rs = 0.66 and rs = 0.62, respectively; p < 0.05). CONCLUSIONS: There are abnormalities in the cortisol axis both at the central level and at the adrenal level early after stroke. Hypercortisolism is closely associated with cognitive disturbances and extensive motor impairment.     

Effects of metyrapone on hypothalamic-pituitary-adrenal axis and sleep in women with post-traumatic stress disorder.

BACKGROUND: Metyrapone blocks cortisol synthesis which results in removal of negative feedback, a stimulation of hypothalamic corticotropin releasing factor (CRF) and a reduction in delta sleep. We previously reported a diminished delta sleep and hypothalamic-pituitary-adrenal (HPA) response to metyrapone in men with post-traumatic stress disorder (PTSD). In this study, we aimed to extend these findings to women. METHODS: Three nights of polysomnography were obtained in 17 women with PTSD and 16 controls. On day 3, metyrapone was administered throughout the day up until bedtime. Plasma adrenocorticotropic hormone (ACTH), cortisol, and 11-deoxycortisol were obtained the morning following sleep recordings the day before and after metyrapone administration. RESULTS: There were no significant between-group differences in hormone concentration and delta sleep at baseline. Relative to controls, women with PTSD had decreased ACTH and delta sleep responses to metyrapone. Decline in delta sleep was associated with the magnitude of increase in ACTH across groups. CONCLUSIONS: Similar to our previous findings in men, the ACTH and sleep electroencephalogram response to metyrapone is attenuated in women with PTSD. These results are consistent with a model of downregulation of CRF receptors in an environment of chronically increased CRF activity or with enhanced negative feedback regulation in PTSD.     

A revised interpretation of postdexamethasone ACTH and cortisol findings in unipolar depressed females

Baseline 8 a.m. adrenocorticotropic hormone (ACTH) and cortisol levels and the postdexamethasone ACTH/cortisol values at 8 a.m. and 4 p.m. were determined in 86 depressed females diagnosed using DSM-III criteria. Postdexamethasone ACTH and cortisol values were significantly correlated with their baseline levels. We have shown that regression analysis should be used to assess dexamethasone-induced changes as the residual ACTH and cortisol responses, with the relative effects of the baseline data on the hormone responses being partialed out. The residual ACTH and cortisol values were significantly increased in the most severely depressed females as compared to minor depressives. The residual ACTH responses were markedly correlated with the residual cortisol responses. Cortisol nonsuppression during a depressive episode appeared to be determined by an augmented ACTH escape from dexamethasone suppression. The residual ACTH and cortisol responses could prove to be the most sensitive reflection of the disorder in the negative feedback by dexamethasone on the pituitary. In clinical practice, the ratio ln (postdexamethasone ACTH): ln (basal ACTH) can be used, since this ratio is linearly correlated with the residual ACTH responses.     

Sub-acute effects of interferon-alpha 2 on adrenocorticotrophic hormone, cortisol, growth hormone and prolactin in humans.

This study investigated the chronic effects of interferon-alpha 2 (IFN-alpha 2) on hormonal secretion in humans. Six patients suffering from chronic hepatitis B or C infection received SC doses of 3 million IU IFN-alpha 2 three times a week for 4 mo. Each patient was examined for hormone secretion four times: the day before initial IFN-alpha 2 administration (day 0), the day of the first injection (day 1), and 4 wk after start of IFN therapy on days 27 (without IFN administration) and 28 (with IFN administration). Adrenocorticotrophic hormone (ACTH), cortisol, growth hormone (hGH), and prolactin (PRL) were measured in plasma samples drawn at 30-min intervals between 1600h and 2400h. Acute administration of IFN-alpha 2 stimulated the release of ACTH to 423% (p = 0.02 vs. day 0) and cortisol to 393% (p = 0.01 vs. day 0) of control values in each patient. In five of the six patients, the plasma levels of hGH were higher on day 1 than on day 0. IFN-alpha 2 did not affect the secretion of prolactin. On day 27, the plasma levels of the four hormones were similar to the baseline levels on day 0. When IFN-alpha 2 was given on day 28, there were no significant differences in the release of ACTH (135% of control, p = 0.4) or cortisol (124% of control, p = 0.5) in comparison to day 27. These findings indicate that IFN-alpha 2 stimulation of hormone release is restricted to specific hormones.(ABSTRACT TRUNCATED AT 250 WORDS)     

The acute effects of a mineralocorticoid receptor (MR) agonist on nocturnal hypothalamic-adrenal-pituitary (HPA) axis activity in healthy controls

INTRODUCTION: Both glucocorticoid and mineralocorticoid receptors (GRs and MRs) help modulate cortisol feedback on the hypothalamic-adrenal-pituitary (HPA) axis. In brain, MRs inhibit the HPA axis and are thought to be fully occupied. Thus, prior studies of the effects of an MR agonist on HPA axis activity have first used metyrapone to inhibit cortisol production and to consequently deplete the receptors. Herein, we propose that an MR agonist may inhibit the HPA axis without first "unloading" receptors of endogenous cortisol. METHODS: Healthy subjects were admitted to the General Clinical Research Center. Blood was sampled for cortisol and adrenocorticotropic hormone (ACTH) from 16:00 to 24:00 h, when greatest MR activity is expected, on two consecutive nights. The first night established a baseline and the second night established response. On the second afternoon, all subjects were given 0.5mg fludrocortisone. Mean cortisol and ACTH were computed from 16:00 to 24:00 h. RESULTS: Fludrocortisone acutely decreased mean cortisol (p=0.003; effect size (ES) 1.65) and mean ACTH (p=0.000, ES 4.46). Additionally, post hoc analysis showed that fludrocortisone tended to decrease the cortisol/ACTH ratio (p=0.0686, ES 0.92) across the same time period. CONCLUSIONS: Fludrocortisone significantly inhibits nocturnal HPA axis activity without first depleting MR receptors with metyrapone. This suggests that brain MRs are not fully occupied by endogenous cortisol and can be further activated by an agonist. The decrease in cortisol/ACTH ratio suggests a possible role on adrenal sensitivity as well. The ability to lower nocturnal HPA axis activity has interesting implications in disorders of HPA axis excess, such as insomnia, depression and healthy aging.     

Hypercortisolemia decreases dexamethasone half-life in rabbit

The pharmacokinetics of dexamethasone have been found to be related to endogenous hypothalamic-pituitary-adrenal (HPA) axis activity. Lower plasma dexamethasone levels in psychiatric patients (especially depressed) who are dexamethasone suppression test (DST) nonsuppressors have previously been reported. Since DST nonsuppression is one measure of HPA axis hyperactivity and is usually associated with relatively increased plasma cortisol levels and lower post dose plasma dexamethasone levels, we hypothesized that hypercortisolemia can induce a more rapid disappearance of dexamethasone from plasma. We therefore studied the kinetics of dexamethasone in rabbits before and after a period of sustained hypercortisolemia produced by administration of IM hydrocortisone acetate, a slowly absorbed salt of cortisol. Mean dexamethasone half-life decreased significantly from baseline of 1.92 h on day zero in seven rabbits to 1.17 h on experimental day 17 of induced hypercortisolemia (P<0.001), while there was no significant change in saline treated controls (n=3). Dexamethasone half-life had returned to the baseline levels when retested 88 days later on experimental day 105. The results indicate that pronounced hypercortisolemia decreases dexamethasone half-life in rabbits, and support the concept that increased circulating cortisol levels induce hepatic enzymes that metabolize dexamethasone. Thus, the lower postdexamethasone plasma dexamethasone levels and decreased dexamethasone half-life in DST nonsuppressors may in part reflect the effect of prior or coincident hypercortisolemia.     

Hypothalamic-pituitary adrenal response to cholecystokinin-B receptor agonism is resistant to cortisol feedback inhibition

Intravenous injection of the cholecystokinin (CCK)-B receptor agonist, pentagastrin, produces robust, dose-dependent release of adrenocorticotropin (ACTH) and cortisol, supporting the hypothesis that CCK-B agonists pharmacologically activate the hypothalamic-pituitary-adrenal (HPA) axis. The mechanism of activation and its physiological relevance remain uncertain. Preliminary data suggest that the ACTH response to pentagastrin may be differentiated from the response to exogenous corticotropin releasing hormone (CRH) by its relative resistance to cortisol feedback inhibition. To more directly test the relationship between cortisol levels and ACTH response to pentagastrin, this study examined responses to pentagastrin (a) during a peak (8 a.m.) and a nadir (4 p.m.) period of endogenous cortisol secretion and (b) when cortisol levels were artificially reduced to low levels by administration of metyrapone. ACTH responses to pentagastrin were identical in the morning and afternoon, despite substantial differences in basal cortisol levels. Suppression of cortisol with metyrapone had little impact on ACTH response to pentagastrin. These data support the hypothesis that CCK-B receptor mediated activation of the HPA axis is relatively resistant to cortisol feedback inhibition. This differentiates it from CRH-mediated activation and raises the possibility that CCK could contribute to acute activation of the HPA axis even in the face of elevated basal cortisol levels, such as those seen in chronic stress or some psychiatric disorders.     

The Dexamethasone Suppression Test for Japanese with Eating Disorders

Abstract: A one-mg oral overnight dexamethasone suppression test (DST) was conducted on 22 inpatients with eating disorders. To confirm that the dexamethasone tablets had been ingested, we measumd the plasma concentrations of dexamethasone the next morning (at 0900 hr after DST). The diagnosis of anorexia nervosa and bulimia was made according to the criteria for DSM-III, respectively. Of the 22 patients with eating disorders, 16 satisfied the criteria for anorexia nervosa and 6 for bulimia. The DST was carried out within 2 weeks of hospitalization on each patient. The subjects were given 1 mg of dexamethasone in the evening (at 2300 hr) and blood samples were collected the following day (at 0900, 1600 and 2100 hr, respectively). The plasma cortisol and dexamethasone levels were concurrently determined by RIA. The criterion for non-suppression was a failure to suppress the plasma cortisol levels below 5.0 μg/dl in any one of the three samples. All but one patient with bulimia had ingested the dexamethasone. Thirteen (62%) of 21 patients with eating disorders were nonsuppressors. We found a significant positive correlation between the plasma cortisol levels at 1600 hr or 2100 hr and a decrease in ideal body weight (n = 16, r = 0.613, p < 0.05; r = 0.75, p < 0.01, respectively) and a significant inverse relationship between the plasma dexamethasone levels at 0900 hr and the plasma cortisol levels at 1600 hr was recognized (n = 21, r - 0.631, p < 0.01). These results suggest that the blood dexamethasone levels as well as body weight might contribute to the abnormalities of DST seen in patients with eating disorders.     

The dexamethasone suppression test for Japanese with eating disorders

A one-mg oral overnight dexamethasone suppression test (DST) was conducted on 22 inpatients with eating disorders. To confirm that the dexamethasone tablets had been ingested, we measured the plasma concentrations of dexamethasone the next morning (at 0900 hr after DST). The diagnosis of anorexia nervosa and bulimia was made according to the criteria for DSM-III, respectively. Of the 22 patients with eating disorders, 16 satisfied the criteria for anorexia nervosa and 6 for bulimia. The DST was carried out within 2 weeks of hospitalization on each patient. The subjects were given 1 mg of dexamethasone in the evening (at 2300 hr) and blood samples were collected the following day (at 0900, 1600 and 2100 hr, respectively). The plasma cortisol and dexamethasone levels were concurrently determined by RIA. The criterion for non-suppression was a failure to suppress the plasma cortisol levels below 5.0 micrograms/dl in any one of the three samples. All but one patient with bulimia had ingested the dexamethasone. Thirteen (62%) of 21 patients with eating disorders were nonsuppressors. We found a significant positive correlation between the plasma cortisol levels at 1600 hr or 2100 hr and a decrease in ideal body weight (n = 16, r = 0.613, p less than 0.05; r = 0.75, p less than 0.01, respectively) and a significant inverse relationship between the plasma dexamethasone levels at 0900 hr and the plasma cortisol levels at 1600 hr was recognized (n = 21, r = 0.631, p less than 0.01). These results suggest that the blood dexamethasone levels as well as body weight might contribute to the abnormalities of DST seen in patients with eating disorders.     

Glucocorticoids and relapse of major depression (dexamethasone/corticotropin-releasing hormone test in relation to relapse of major depression).

BACKGROUND: Knowledge of pathogenic mechanisms and predictors of relapse in major depressive disorder is still limited. Hypothalamic-pituitary-adrenocortical (HPA) axis dysregulation is thought to be related to the development and course of depression. METHODS: We investigated whether dexamethasone/corticotropin-releasing hormone (DEX/CRH) test parameters were related to the occurrence of relapse in 45 outpatients with clinically remitted major depression. The DEX/CRH test was administered before and after 8 weeks of antidepressant treatment. RESULTS: Posttreatment maximal adrenocorticotropic hormone (ACTH) and maximal cortisol levels, as well as delta ACTH and delta cortisol levels, were significantly higher (all p < .05) among patients who relapsed (n = 22) compared with patients in whom no relapse occurred (n = 23). Higher posttreatment maximal cortisol response on the DEX/CRH test was associated with shorter "relapse-free survival" (p = .05). CONCLUSIONS: In outpatients with clinically remitted major depression, higher posttreatment maximal cortisol levels on the DEX/CRH test were associated with relapse of major depression.     

Plasma dexamethasone levels in children given the dexamethasone suppression test

To determine whether children who demonstrate dexamethasone suppression test (DST) nonsuppression have lower plasma dexamethasone levels than DST suppressors, we administered the DST to 73 patients ranging in age from 5-14 years. Plasma dexamethasone levels and postdexamethasone cortisol levels were measured at 4:00 PM on day 2. We found: (1) DST nonsuppressors had significantly lower plasma dexamethasone levels (p less than 0.03) than suppressors; similar trends were observed when the population was divided into depressed and nondepressed patients; (2) mg/m2 dose of dexamethasone was directly correlated with plasma dexamethasone (p less than 0.003) and inversely correlated with postdexamethasone plasma cortisol levels (p less than 0.04); and (3) a statistically significant inverse correlation between plasma dexamethasone levels and postdexamethasone cortisol levels (p less than 0.04). Our findings show that plasma dexamethasone levels are important in evaluating DST results in psychiatrically disturbed children and suggest that dexamethasone dosage for use in the DST in children might be better calculated in terms of body surface area.     

Salivary cortisol levels and their correlation with plasma ACTH levels in depressed patients before and after the DST.

OBJECTIVE: The aim of this work was to study the clinical utility of salivary cortisol concentrations in a group of depressed patients undergoing the dexamethasone suppression test (DST) and the correlation of these concentrations with plasma ACTH levels. METHOD: Twenty outpatients from the psychiatric department of a Barcelona hospital who were diagnosed as having nonendogenous (N = 9) or endogenous (N = 11) depression according to DSM-III criteria and the Newcastle scale participated in the study. The comparison group consisted of 12 healthy volunteers. Blood and saliva samples were taken before and after administration of 1 mg of dexamethasone Salivary cortisol and plasma ACTH concentrations were determined by direct iodine-125 radioimmunoassay with commercial kit reagents. RESULTS: Predexamethasone salivary cortisol concentrations were significantly higher in the group with endogenous depression than in the comparison group. A significant correlation was obtained between plasma ACTH and predexamethasone salivary cortisol levels in the group with nonendogenous depression and in the comparison subjects. CONCLUSIONS: These preliminary findings indicate that salivary cortisol could substitute for plasma cortisol in clinical studies in which the DST and hypercortisolemia are evaluated. The lack of correlation between ACTH and cortisol levels in saliva in the group of endogenously depressed patients could indicate a disturbance in the regulation of cortisol secretion in major depression.     

Acute HPA axis responses, heart rate, and mood changes to psychosocial stress (TSST) in humans at different times of day

There is evidence showing that HPA axis responses to pharmacological provocation depend on time of day with larger cortisol responses in the afternoon and evening compared to the morning hours. However, it is still unknown whether HPA axis responses to psychological stress are affected by time of day and whether they can be assessed with equal reliability in the morning and afternoon, respectively. The present reanalysis is based on five independent studies conducted in the same laboratory by and. All subjects were confronted with the Trier Social Stress Test (TSST) either in the morning or in the afternoon. The total sample consisted of 180 adults with 115 younger (49 females, 66 males) and 65 older adults (32 females, 33 males). All ANCOVA results controlled for possible age and gender effects. Stress-related free salivary cortisol, total plasma cortisol and ACTH net increases did not differ according to time of day (all p = n.s.). However, as expected pre-stress free salivary and total plasma cortisol levels differed significantly between the morning and afternoon group (both p < 0.005), leading to a significantly higher free cortisol area under the curve (AUC) in the morning (p = 0.02). Taken together, these observations suggest that the adrenal glands may be more sensitive to ACTH in the morning. Additionally, higher basal salivary cortisol levels were related to a lower stress-related net increase in salivary cortisol (p = 0.02), total plasma cortisol (p < 0.0001), and marginally ACTH (p = 0.09). Stress-related heart rate increases did not differ between groups (p = n.s.). The finding that the TSST-induced mood change was differentially affected by time of day requires further exploration. We conclude that comparable HPA axis and heart rate stress responses to psychosocial stress can be measured in the morning and afternoon.