Role of peripherally infused angiotensin II on the human hypothalamic–pituitary–adrenal axis

Although angiotensin II (AII), a potent vasoconstrictor agent, has been reported to stimulate the hypothalamic-pituitary-adrenal (HPA) axis of laboratory animals, its role in the regulation of this axis in humans appears to be controversial. To examine this question, AII (Val5-AII amide) was infused intravenously into 19 male normal volunteers at the doses of 0, 1, 3.3 and 10 ng/kg/min for 30 min. AII had no effect on plasma ACTH, cortisol, corticotrophin-releasing hormone, arginine vasopressin, and atrial natriuretic factor concentrations, nor did it increase systolic or diastolic arterial blood pressure. On the other hand, AII caused a dose-dependent increase of plasma aldosterone concentrations, suggesting that the doses and the mode of AII infusion were effective. Thus, our data show that peripherally infused AII has no detectable effect on the HPA axis function in humans, at doses capable of stimulating plasma aldosterone secretion, its specific target hormone.     

The short Synacthen and insulin stress tests in the assessment of the hypothalamic–pituitary–adrenal axis

OBJECTIVE The best dynamic test for the assessment of the hypothalamic–pituitary–adrenal axis and the interpretation of the cortisol levels, remain a matter of controversy. We aimed to establish normal ranges with current assays, for both the short Synacthen (SST) and insulin stress tests (IST) and then to use these data to examine whether the SST can satisfactorily substitute for the IST in assessment of the hypothalamic–pituitary–adrenal axis. DESIGN Thirty SSTs and 27 ISTs were performed on different healthy volunteers. The results of all paired tests performed on patients in the last three years are reviewed. SETTING Programmed Investigation Unit. SUBJECTS Fifty-seven healthy volunteers and 166 patients. MAIN OUTCOME MEASURES Basal serum cortisol concentration and cortisol values obtained at 30 and 60 minutes during the SST compared to the maximum obtained with adequate hypoglycaemia (plasma glucose < 2mmol/l) during an IST. RESULTS From normal data the mean-2SD 30-minute value during the SST was 392 nmol/l and 60-minute value was 497 nmol/l. The maximal cortisol response (mean ? 2SD) during the IST was 519 nmol/l. Sixty patients failed the IST, none of whom had a basal cortisol > 450 nmol/l and only six (10%) had a 30-minute cortisol value > 600 nmol/l. The 30-minute value provided a better index than the 60-minute value. The basal, 30 and 60-minute values during the SST all correlated positively and significantly with the maximal cortisol on IST. The correlations persisted for all microadenomas and macroadenomas secreting prolactin, gonadotrophins or growth hormone, patients undergoing either pre or post-adenomectomy evaluation, and in those patients who had received long-term steroids provided that the medication had been reduced and stopped two days prior to admission. CONCLUSIONS Using a 30-minute cortisol value > 600 nmol/l as a cut-off, the short Synacthen test provides a suitable substitute for the insulin stress test. Adopting this policy will decrease the number of insulin stress tests performed by one-quarter and thus provide a substantial saving without detriment to patient care.     

A low dose ACTH test to assess the function of the hypothalamic–pituitary–adrenal axis

OBJECTIVE  The insulin tolerance test (ITT) has long been used to assess the hypothalamic–pituitary–adrenal axis, but may be hazardous. The standard synthetic ACTH (Synacthen) test has been advocated as a substitute but is sometimes insensitive. In this study the ITT has been compared to a low dose ACTH stimulation test (1 μg) and the standard ACTH stimulation test (250 μg).
SUBJECTS  Twenty-seven subjects were studied, 24 with verified or suspected hypothalamic–pituitary disorders and three on long-term glucocorticoid therapy.
DESIGN  Insulin tolerance, low dose ACTH and standard ACTH tests were performed in all patients. The ITT was performed less than 48 hours after the ACTH tests. Synacthen was administered as an intravenous bolus.
MEASUREMENTS  Serum cortisol values were determined by radioimmunoassay. The peak cortisol value during ITT was compared to the cortisol levels during the ACTH tests.
RESULTS  There was a highly significant correlation between peak cortisol values during ITT and cortisol levels after 20–60 minutes in the low dose ACTH test ( r _s = 0.91–0.93; P < 0.0001) and after 30 and 60 minutes in the standard ACTH test ( r _s= 0.85 and 0.89 respectively; P < 0.0001). Four patients showed discrepancies between the three tests.
CONCLUSIONS  The 1-μg ACTH test follows the ITT more closely and may be more sensitive than the standard ACTH test in detecting more subtle insufficiency of the hypothalamic–pituitary–adrenal axis. The standard ACTH test and the insulin tolerance test may thus be replaced by the 1-μg ACTH test in screening for secondary cortisol insufficiency. We recommend that serum cortisol is measured before and 30 and 40 minutes after the ACTH injection.     

The effects of interleukin-2 treatment on endothelin and the activation of the hypothalamic–pituitary–adrenal axis

OBJECTIVE: Recent reports suggest that complex interactions exist between the neuroendocrine and immune systems. It has been shown for example that cytokines are able to stimulate the hypothalamo-pituitary-adrenal axis. In addition, some studies present evidence that endothelin is able to modulate the activity of several hypothalamic-pituitary axes, e.g. by inducing the ACTH production. DESIGN: We investigated the effects of interleukin-2 on endothelin levels and the hypothalamo-pituitary-adrenal axis. We determined the interleukin-6, big-endothelin, endothelin-1, ACTH, cortisol and AVP responses to intravenously and subcutaneously administered interleukin-2 in 8 cancer patients in a randomized placebo controlled trial. PATIENTS: 8 Patients (2 female and 6 male), age 44 +/- 4.8 years, were enrolled. All patients had a World Health Organization performance status of 1 or less and a Karnofsky Index of at least 80%. MEASUREMENTS: Blood-samples were taken before and 15, 30, 45, 60, 120, 180, 240, 300 and 360 min after interleukin-2 injection. Cytokine serum levels and the plasma levels of big-endothelin, endothelin, ACTH and AVP were analysed using radioimmuno-assays. Cortisol was assayed by an enzyme-linked immunosorbent assay. RESULTS: Interleukin-2 treatment significantly increased plasma big-endothelin levels (P < 0.01 vs basal) and endothelin-1 levels (P < 0.05 vs basal) within two hours and this was followed by an increase in ACTH (P < 0.01 vs basal) and cortisol (P < 0.05 vs basal) within three hours. Interleukin-6 levels increased two hours after interleukin-2 administration (P < 0.01 vs basal). Interleukin-2 had no detectable effect on AVP, blood pressure or heart rate. CONCLUSIONS: Our data demonstrate that cytokines are able to activate the human hypothalamo-pituitary-adrenal axis in vivo. On the basis of the observed time kinetics and in connection with previous findings from in vitro and animal models, we conclude that endothelin may be a link between cytokines and corticotrophin-releasing hormone, most probably functioning as a cytokine-induced neuromodulator controlling pituitary functions.     

Effect of carbenoxolone on the plasma renin activity and hypothalamic–pituitary–adrenal axis in congenital adrenal hyperplasia due to 21-hydroxylase deficiency*

OBJECTIVE: To test the hypothesis that carbenoxolone, an inhibitor of 11beta-hydroxysteroid dehydrogenase, might augment the ACTH-suppressing and mineralocorticoid activities of hydrocortisone without a corresponding increase in peripheral hydrocortisone effects, we assessed the effects of carbenoxolone in patients with congenital adrenal hyperplasia. DESIGN AND PATIENTS: Six patients with classic 21-hydroxylase deficiency (5 salt-losing, 1 nonsalt-losing) were enrolled in this study. The study protocol involved 3 treatment periods (except for patient 3): phase 1, hydrocortisone and fludrocortisone; phase 2, hydrocortisone, fludrocortisone and carbenoxolone; phase 3, hydrocortisone and carbenoxolone. Patient 3 was not treated with fludrocortisone at baseline, so she participated only in phase 1 (hydrocortisone only) and phase 2 (hydrocortisone and carbenoxolone). Hydrocortisone and fludrocortisone dosages were kept the same during the study except for the discontinuation of fludrocortisone during phase 3. MEASUREMENTS: Plasma adrenal androgens or their precursors (androstenedione, 17-hydroxyprogesterone, and testosterone, and urine pregnanetriol); plasma cortisol, cortisol-binding globulin, ACTH, apparent cortisol metabolic clearance, 24-h urine 17-hydroxysteroids, and urine free cortisol; mineralocorticoid activity, as measured by plasma renin activity, body weight, plasma potassium, and mean blood pressure; fasting insulin/glucose ratio, protein balance, % eosinophils in peripheral blood, and total urine pyridinoline and deoxypyridinoline; TRH stimulation of TSH and pyridostigmine/GHRH stimulation of growth hormone. RESULTS: Compared to phase 1, the addition of carbenoxolone (with or without concurrent fludrocortisone administration) produced statistically significant decreases of 20-50% in mean plasma 17-hydroxyprogesterone, androstenedione, and renin activity. Since carbenoxolone also decreased the apparent metabolic clearance rate of cortisol by 20%, other measures of systemic glucocorticoid activity were examined. Carbenoxolone did not produce a cushingoid appearance or increase body weight, blood pressure, blood glucose or plasma insulin levels. Carbenoxolone also did not suppress stimulated GH levels, but did decrease TRH-stimulated TSH levels by approximately 20% (P < 0.05). CONCLUSION: Carbenoxolone can augment the adrenal androgen-suppressing activity of hydrocortisone in patients with 21-hydroxylase deficiency. These observations support the hypothesis that selective inhibition of enzymes that metabolize cortisol may lead to new approaches to improve the treatment of congenital adrenal hyperplasia.     

Fat distribution in obese women is associated with subtle alterations of the hypothalamic–pituitary–adrenal axis activity and sensitivity to glucocorticoids

OBJECTIVES: Obesity with abdominal body fat distribution (A-BFD) and hypothalamic-pituitary-adrenal (HPA) axis activity are somehow linked, but the exact interactions still need clarification. Obese subjects display normal circulating plasma cortisol concentrations with normal circadian rhythms. However, when the HPA axis is pharmacologically challenged, body fat distribution matters and then A-BFD obese women differ from those with subcutaneous body fat distribution (P-BFD). We hypothesized that lower dose provocative and suppressive tests than those used to diagnose hypercortisolism of tumour origin or adrenal insufficiency would shed some light on the characteristics of the HPA axis activity in relation with body fat distribution. PATIENTS AND METHODS: Fifty premenopausal obese women were grouped according to their body fat mass distribution. Their plasma cortisol responses to (i) two low doses of dexamethasone (0.25 and 0.5 mg) with (ii) low dose of the ACTH analogue tetracosactrin (1 microg) were assessed. Salivary cortisol was also determined during the ACTH test. RESULTS: A-BFD differed from P-BFD women in terms of HPA axis responsiveness. They had comparatively: (i) increased nocturnal cortisol excretion (9.38 +/- 2.2 vs. 6.82 +/- 0.91 nmol/micromol creatinine, A-BFD vs. P-BFD, respectively, P = 0.03); (ii) increased salivary cortisol response to ACTH stimulation (1 microg) [salivary cortisol peak: 33.4 (14.1-129) vs. 28.5 (13.2-42.8) nmol/l; salivary AUC: 825 (235-44738) vs. 537 (69-1420) nmol/min/l; A-BFD vs. P-BFD, P = 0.04 for both]; and (iii) increased pituitary sensitivity to dexamethasone testing [postdexamethasone (0.25 mg) plasma cortisol levels: 163 (26-472) vs. 318 (26-652) nmol/l and postdexamethasone (0.5 mg) plasma cortisol levels: 26 (26-79) vs. 33 (26-402) nmol/l; A-BFD vs. P-BFD, P = 0.01 for both). CONCLUSIONS: These data demonstrate differences in the HPA axis activity and sensitivity to glucocorticoids between obese women differing in their body fat distribution, with both enhanced negative and positive feedback in those with abdominal obesity. Several mechanisms may explain these differences: central vs. peripheral hypotheses. Thus, abdominal obesity does not appear to be linked solely to one pathophysiological hypothesis.     

The effect of chronic hexarelin administration on the pituitary–adrenal axis and prolactin

OBJECTIVE: With the development of growth hormone (GH) releasing agents and their use in human subjects, it is clear that these agents are not specific for GH release. More recent studies in humans have demonstrated acute increases in adrenocorticotrophic hormone (ACTH), cortisol and prolactin (PRL) after boluses of intravenous or subcutaneous GHRPs. The potential adverse effects of repeated episodes of transient hyperprolactinaemia and hypercortisolaemia during long-term therapy with growth hormone releasing peptides (GHRPs) and similar agents have raised concern. We have therefore assessed the impact of chronic hexarelin administration on the pituitary-adrenal axis and serum prolactin levels. DESIGN: Each subject received twice-daily subcutaneous hexarelin therapy (1.5 micrograms/kg body weight) for 16 weeks. The ACTH, cortisol and PRL responses to the morning subcutaneous injection of hexarelin were assessed. Hexarelin was administered at time 0 and blood samples were taken at -10, 0, 10, 20, 30, 40, 50, 60, 90, 120, 170 and 180 min. The ACTH and PRL responses were assessed at baseline and after 16 weeks of therapy. The cortisol response was assessed at baseline, 16 weeks and also 4 weeks after completion of hexarelin therapy. Basal levels of cortisol binding globulin (CBG), 24-h urinary free cortisol (UFC) estimations, thyroid stimulating hormone (TSH) and total thyroxine (TT4) were performed at baseline, weeks 16 and 20. RESULTS: The mean (+/- SEM) area under the cortisol curve (AUCCORT) at baseline, week 16 and week 20 were 1506 (+/- 77) nmol/l/h, 1222 (+/- 92) nmol/l/h and 1586 (+/- 58) nmol/l/h, respectively. There was a significant change in AUCCORT over the study period (P = 0.008). Compared with baseline, AUCCOPRT had decreased significantly (P < 0.05) after 16 weeks of hexarelin therapy. Four weeks after completion of hexarelin therapy, the AUCCORT increased significantly compared with AUCCORT at week 16 (P < 0.01) and was no longer significantly different from baseline values. There were no significant changes in UFC (P = 0.3), basal cortisol measurements (P = 0.19), area under the ACTH curve (AUCACTH) (P = 0.24) or CBG (P = 0.6) over the study period. The mean (+/- SEM) area under the PRL curve (AUCPRL) at the baseline and week 16 were 624 (+/- 82) mU/l/h and 641 (+/- 83) mU/l/h, respectively. There was no significant change in AUCPRL over the study period (P = 0.35). CONCLUSION: The present study demonstrates clearly that in this hexarelin dosage regimen, over-stimulation of the pituitary adrenal axis and prolactin secretion do not occur. In fact the impact of chronic hexarelin therapy on the pituitary-adrenal axis, i.e. decreased AUCCORT, contradict the findings reported after acute hexarelin administration and cannot be explained by changes in CBG. The lack of change in UFC, however, suggests that these changes are unlikely to be of clinical significance although the underlying mechanism requires further study.     

Immunoreactive corticotropin-releasing factor is present in human maternal plasma during the third trimester of pregnancy

Immunoreactive (IR) corticotropin-releasing factor (CRF)-like activity was detectable in the majority of plasma samples obtained from women in the third trimester of pregnancy (68.7 +/- 23.6 pg/ml (14.4 +/- 4.9 fmol/ml); mean +/- SE, n = 15), but not in plasma (less than 10 pg/ml) from first (n = 9) or second (n = 11) trimester of pregnancy, 1 day post partum (n = 7), non-pregnant women (n = 10), or in plasma obtained from patients with Cushing's disease (n = 2) or Nelson's syndrome (n = 1), or in basal (n = 6) or ether-stressed (n = 6) rat plasma. Gel filtration of third trimester pooled plasma revealed that the majority of such material eluted with Kav of rat CRF (1-41). The IR CRF (1-41)-sized material eluted with the identical retention time as rat CRF in a reverse phase high performance liquid chromatography (HPLC) system. The detection of IR CRF exclusively in third trimester maternal plasma, together with our previous demonstration that material physicochemically indistinguishable from it is present in human term placental extracts, suggests that the placenta may be the source of plasma IR CRF.     

Sleep deprivation effects on the activity of the hypothalamic–pituitary–adrenal and growth axes: potential clinical implications

OBJECTIVES: Although several studies have shown that sleep deprivation is associated with increased slow wave sleep during the recovery night, the effects of sleep deprivation on cortisol and growth hormone (GH) secretion the next day and recovery night have not been assessed systematically. We hypothesized that increased slow wave sleep postsleep deprivation is associated with decreased cortisol levels and that the enhanced GH secretion is driven by the decreased activity of the HPA axis. DESIGN AND SUBJECTS: After four consecutive nights in the Sleep Laboratory, 10 healthy young men were totally deprived of sleep during the fifth night, and then allowed to sleep again on nights six and seven. Twenty-four hour blood sampling was performed serially every 30 minutes on the fourth day, immediately following the previous night of sleep and on the sixth day, immediately after sleep deprivation. MEASUREMENT: Eight-hour sleep laboratory recording, including electroencephologram, electro-oculogram and electromyogram. Plasma cortisol and GH levels using specific immunoassay techniques. RESULTS: Mean plasma and time-integrated (AUC) cortisol levels were lower during the postdeprivation nighttime period than on the fourth night (P < 0.05). Pulsatile analysis showed significant reduction of both the 24 h and daytime peak area (P < 0.05) and of the pulse amplitude (P < 0.01), but not of the pulse frequency. Also, the amount of time-integrated GH was significantly higher for the first 4 h of the postdeprivation night compared to the predeprivation night (P < 0.05). Cross-correlation analyses between the absolute values of the time-series of each hormone value and percentage of each sleep stage per half hour revealed that slow wave sleep was negatively correlated with cortisol and positively correlated with GH with slow wave sleep preceding the secretion of these hormones. In contrast, indices of sleep disturbance, i.e. wake and stage 1 sleep, were positively correlated with cortisol and negatively correlated with GH. CONCLUSION: We conclude that sleep deprivation results in a significant reduction of cortisol secretion the next day and this reduction appears to be, to a large extent, driven by the increase of slow wave sleep during the recovery night. We propose that reduction of CRH and cortisol secretion may be the mechanism through which sleep deprivation relieves depression temporarily. Furthermore, deep sleep has an inhibitory effect on the HPA axis while it enhances the activity of the GH axis. In contrast, sleep disturbance has a stimulatory effect on the HPA axis and a suppressive effect on the GH axis. These results are consistent with the observed hypocortisolism in idiopathic hypersomnia and HPA axis relative activation in chronic insomnia. Finally, our findings support previous hypotheses about the restitution and immunoenhancement role of slow wave (deep) sleep.     

Fetal and maternal sheep hypothalamus pituitary adrenal axis responses to chronic binge ethanol exposure during the third trimester equivalent

BACKGROUND: We tested the hypothesis that in utero ethanol exposure results in changes in fetal and maternal adrenocorticotropin (ACTH) and cortisol during the third trimester equivalent, by using a chronically instrumented fetal sheep model. METHODS: Pregnant ewes received saline or ethanol intravenously 3 consecutive days per week from day 109 to day 132 of gestation. Fetal and maternal blood samples were collected on days 118 and 132. RESULTS: Maternal and fetal ACTH and cortisol values increased on days 118 and 132 of gestation in response to ethanol infusions that created blood ethanol concentrations (BECs) that are easily achievable by human drinkers. Peak ACTH and cortisol values were detected 30 to 60 min after peak BECs were achieved. CONCLUSIONS: Chronic ethanol exposure during the third trimester equivalent in sheep resulted in repeated activation of the hypothalamus-pituitary-adrenal axis in both the mother and fetus. Temporally, the patterns of maternal and fetal responses to ethanol infusion were similar. We conclude that ovine maternal ethanol exposure during the third trimester equivalent increases fetal ACTH and cortisol concentrations, hormonal responses that may play a role in mediating alcohol-related birth defects.     

Detection of maternal cells in human fetal blood during the third trimester of pregnancy using allele-specific PCR amplification

Using a highly sensitive allele-specific PCR amplification method, we have previously shown that maternal cells could be detected in all 10 cord bloods tested. This raised the question of whether maternal cells are released into cord blood during the process of delivery or whether they are already present during pregnancy. We have now used the same PCR method to detect the presence of maternal cells in nine fetal blood samples collected at different gestational ages. Maternal cells were detected in eight samples obtained between 24 and 35 weeks of gestation. They were estimated to amount between 10⁻⁴ and 10⁻⁵ of nucleated fetal blood cells. In two cases mononuclear and polymorphonuclear cell fractions were separated by Ficoll gradient centrifugation and maternal cells were detected as comparable levels in both fractions. Maternal cells could not be detected in the one fetal blood sample obtained at 20 weeks of gestation, suggesting that maternal cells could appear at detectable levels in fetal blood during the third trimester of pregnancy. These results are discussed in terms of materno-fetal immune tolerance and of transmission of viruses (and more specifically of the human immunodeficiency virus) from mother to child.     

Impaired glucose tolerance in the third trimester of pregnancy

When the methods and interpretation of glucose tolerance as recommended by the World Health Organisation were applied to 247 patients in the third trimester of pregnancy selected on account of glycosuria, previous large-for-dates offspring, diabetic family history, maternal obesity or a fetus large for gestational age, impaired glucose tolerance (IGT) was found in 20 (8.1%). Patients with IGT were older than those with normal tests: 30.5 +/- 4.8 years (mean +/- S.D.) vs 27.8 +/- 4.8 years (p less than 0.02) and more having IGT had a first degree family history of diabetes (25% vs 10%, p less than 0.05). The majority (15) of the IGT patients then received dietary advice to restrict refined carbohydrate. Post-prandial blood glucose and HbA1 concentrations in these subjects remained within the normal range except for one patient who was treated with insulin. Pregnancy outcome was satisfactory in the patients with impaired tolerance and further studies will be required to assess the clinical significance of IGT in pregnancy.     

Steady-state lopinavir levels in third trimester of pregnancy

Stek and colleagues reported low lopinavir levels in the third trimester of pregnancy at standard dosing. Since their initial report in 2003, we have taken steady-state trough lopinavir levels in all pregnant women in the third trimester; the results of 26 women on a lopinavir/ritonavir regimen are reported. The median trough level was 3.66 microg/ml, range 0.25-9.97; the median HIV viral load was 49 copies/ml at delivery. All infants were HIV polymerase chain reaction negative at 3 months.     

Acute hepatitis C during the third trimester of pregnancy

A pregnant woman presented at 32 weeks of amenorrhea with jaundice secondary to acute hepatitis C. Spontaneous delivery took place 3 days later. The infant's serum tested negative for C viral RNA 6 months after delivery. Treatment with high doses of interferon-alpha for a period of 4 weeks was begun 4 days after delivery. Although a virological response was noted at the end of the treatment, the hepatitis relapsed and progressed toward chronicity. Case reports of acute hepatitis C during pregnancy are very rare, as the methods used for the follow-up of pregnant women render the diagnosis of asymptomatic forms difficult. In one case, the acute hepatitis C was severe. The occurrence of acute hepatitis C during pregnancy seems to increase the risk of premature delivery, but not that of vertical transmission. Given the frequency of side effects, it seems preferable not to begin interferon treatment until after delivery.     

Evidence for increased metabolism of chloroquine during the early third trimester of human pregnancy

OBJECTIVE: To examine the possibility of a different extent of chloroquine (CQ) metabolism in human pregnancy by determining blood level profiles of the drug and its major metabolite, desethylchloroquine (CQM). METHODS: Five women in the early third trimester of pregnancy and five non-pregnant women received each a single 600 mg oral dose of CQ and blood samples were collected at pre-determined intervals following drug administration. Plasma concentrations of CQ and CQM were analysed by an established HPLC method. RESULTS: The C(max) and AUC(0-48 h) of CQM were significantly higher in the pregnant than the non-pregnant group (P = 0.009). The ratio AUC(CQ)/AUC(CQM) ranged from 0.09 to 0.35 among pregnant women, and from 1.70 to 4.81 among non-pregnant women. CONCLUSION: Results from this preliminary study indicate an occurrence of induction of metabolism of CQ in the early third trimester of pregnancy. In view of toxicological importance of CQ metabolites, it is suggested that caution should be exercised in evaluation of higher dosage regimen of CQ in pregnant women.