Plasma Free Cortisol Research Articles

Corticosteroid-binding globulin (CBG) production by hepatic and extra-hepatic sites in the ovine fetus; effects of CBG on glucocorticoid negative feedback on pituitary cells in vitro

Plasma cortisol levels increase in fetal sheep during late gestation and this is associated with an increase in plasma corticosteroid-binding globulin (CBG) concentrations. However, the relative tissue sources of plasma CBG, the ontogeny of its biosynthesis and glycoform composition have not been established in the ovine fetus. Therefore we examined whether changes in plasma corticosteroid binding capacity (CBC) in fetal sheep during late gestation were associated with different patterns of glycosylation and reflected changes in tissue CBG expression. Since free cortisol is considered the bioactive fraction, we measured changes in the percent and absolute free cortisol in fetal plasma during late gestation. In order to examine whether CBG alters cortisol negative feedback at the level of the fetal pituitary, we also examined the effect of exogenous CBG in mediating the glucocorticoid-induced suppression of basal and corticotrophin-releasing hormone (CRH)-stimulated ACTH release from fetal pituitary cells in culture. The mean free cortisol concentration in plasma was not different between days 15 and 20 prior to parturition, and between 5 and 10 days prepartum, although it did rise between these times. Plasma CBC in chronically catheterized fetuses rose from 23.3 +/- 4.6 ng/ml at day 115 to 86.5 +/- 20.8 ng/ml at term and then decreased rapidly after birth. Between day 125 and day 140 of pregnancy approximately 10% of fetal plasma CBG was retarded by Concanavalin-A chromatography. This proportion increased at birth and attained adult values of > 70% by one month of age. By Northern blotting the relative levels of CBG mRNA in the fetal liver did not change between days 100 and 125, then increased significantly at day 140, but declined at term and in newborn lambs. CBG mRNA was undetectable in total RNA from lung, kidney, hypothalamus and placentomes, but was present in the fetal pituitary at days 125 and 140. Reverse transcription-PCR was used to confirm the presence of CBG mRNA in pituitary tissue from term fetuses. In cultures of term fetal pituitary cells, added CBG attenuated the cortisol- but not the dexamethasone-mediated suppression of basal and CRH-stimulated ACTH release. We conclude that in fetal sheep there is an increase in the corticosteroid binding capacity of plasma during late pregnancy which regulates, in part, free cortisol levels in the circulation. The liver is the major site of CBG biosynthesis in the fetus and at least until day 140 of gestation the rise in plasma CBC is associated with an increase in hepatic CBG mRNA levels.(ABSTRACT TRUNCATED AT 400 WORDS)

Total cortisol, free cortisol, and growth hormone associated with brief social separation experiences in young macaques

Many behavioral, immunological, and physiological consequences or brief maternal separation in bonnet (Macaca radiata) and pigtail monkeys (Macaca nemistrina) have been documented. However, the impact of social separation on plasma cortisol and growth hormone is unknown for these particular species. In the present study, the behavioral and endocrinological consequences of a 2-week maternal separation in socially housed infant bonnet and pigtail monkeys were followed. In seven pairs (separated and matched control) of bonnet and six pairs of pigtail infants, plasma was obtained under baseline, separated, and reunion conditions twice weekly for the duration of the study. Blood samples were obtained from both infants of the pair in approximately 10 min. Plasma total cortisol, free cortisol, and growth hormone were measured in these samples. Focal animal behavioral observations were made on all subjects twice daily throughout the study period. In both species, total cortisol and free cortisol rose immediately following maternal separation in comparison to the matched nonseparated controls and returned to basal levels (e.g., that of matched nonseparated controls) following reunion with the mother. In contrast, plasma growth hormone rose only in the pigtail infants over a time course that peaked around the time of reunion. Multiple regression techniques indicated for the first week of separation, in the separated but not control subjects, that mean plasma free and total cortisol was positively related to distress behaviors (vocalization and postural slouch) observed during this week and negatively related to social behaviors (play and proximity to others) noted during the same period. In contrast, plasma growth hormone was related to both species and sex of the subjects but unrelated to behavioral variables.

Increased free cortisol in plasma of dogs with portosystemic encephalopathy (PSE)

Dogs with portosystemic encephalopathy (PSE) are known to develop pituitary-dependent hyperadrenocorticism, but there have been no reports on the plasma protein binding of cortisol in these dogs. Since the liver is involved in the synthesis of corticosteroid-binding globulin (CBG) and other transport proteins for cortisol, the binding characteristics of these proteins and thus the biologically-active free fraction of cortisol might be altered in dogs with PSE. We investigated the total concentration of cortisol and the free fraction and the free cortisol concentration in plasma of thirty-two dogs with PSE due to inherited portosystemic shunts or chronic active hepatitis with cirrhosis. We found a significantly higher free fraction (14.7 ± 5.8%, P<0.0001) and free cortisol concentration (26.3 ± 23.1 nM, P<0.001) in these dogs than in healthy controls (8.2 ± 2.3% and 9.2 ± 7.2 nM, respectively). Moreover, basal concentrations of total cortisol in the dogs with PSE were higher than in the healthy controls (190 ± 146 nM v. 107 ± 65, P<0.01). The per cent free cortisol in plasma was not significantly correlated with the concentration of albumin or the total cortisol in plasma. We conclude that there is decreased binding of cortisol in plasma of dogs with PSE due to decreased hepatic synthesis of cortisol binding proteins. The presence of increased concentrations of free cortisol in these dogs indicates that their basal pituitary-adrenocortical activity was increased, probably due to aberrant neurotransmission in brain centers associated with pituitary function, as a result of hepatic encephalopathy.

The Cushing Syndrome Induced by Atrial Natriuretic Peptide-Producing Thymic Carcinoid

Letters1 July 1994The Cushing Syndrome Induced by Atrial Natriuretic Peptide-Producing Thymic CarcinoidShuichi Okada, MD, Kihachi Ohshima, MD, and Masatomo Mori, MDShuichi Okada, MDGunma University of School of Medicine; Showa-machi, Maebashi 371; JapanSearch for more papers by this author, Kihachi Ohshima, MDGunma University of School of Medicine; Showa-machi, Maebashi 371; JapanSearch for more papers by this author, and Masatomo Mori, MDGunma University of School of Medicine; Showa-machi, Maebashi 371; JapanSearch for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/0003-4819-121-1-199407010-00025 SectionsAboutFull TextPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail TO THE EDITOR:A 75-year-old Japanese man was hospitalized for hypokalemia. Levels of plasma adrenocorticotropic hormone (ACTH) and free cortisol in urine were elevated to 220 pg/mL (normal, 9 to 52 pg/mL) and 793 mg/d (normal, 30 to 100 mg/d), respectively. Blood concentration of corticotropin-releasing factor was 13.8 pg/mL (normal, <40 pg/mL). Chest radiographs and computed tomographic examinations showed an enlarged thymic gland and normal-sized adrenal glands. Venous samplings in the superior and inferior vena cava at several levels showed markedly increased plasma atrial natriuretic peptide concentrations near the thymic tumor (from 120 to 620 pg/mL). By contrast, plasma ACTH ...

The effects of the acute administration of RU 486 on dietary fat preference in fasted lean and obese men

The effects of RU 486, a potent glucocorticoid antagonist, on dietary fat preference were explored in obese men and lean controls in a double-blind crossover study. An oral 10 mg/kg dose of RU 486 or placebo was administered at midnight the second night of a 48-h hospital stay. Macronutrient and caloric intakes were calculated each day and a taste test of six commercial dairy products (fat content by weight <0.5%, 2.0%, 3.3%, 10.5%, 18%, and 36%) was performed. Dairy products were judged for pleasantness, creaminess, and overall preference. Subjects were then asked to consume their favorite dairy product until sated. Urinary free cortisol (UFC) and plasma adrenocorticotropic hormone (ACTH), cortisol, insulin, and glucose were determined. Intake of a self-selected diet was recorded. As expected, in response to RU 486, UFC increased from 120 ± 25 μg/24 h to 297 ± 73 μg/24 h ( p < 0.05) in obese men and from 81 ± 10 μg/24 h to 357 ± 109 μg/24 h ( p < 0.05) in lean men. Plasma cortisol increased from 26.1 ± 1.1 μg/dl to 31.8 ± 1.0 μg/dl ( p < 0.05) in obese men and from 26.1 ± 1.7 μg/dl to 32.2 ± 1.7 μg/dl ( p < 0.05) in lean men. Plasma insulin was significantly higher in obese 24.6 ± 3.2 μIU/ml than in lean men 12.8 ± 1.1 μIU/ml ( p = 0.0001) but was unaffected by RU 486. RU 486 did not decrease fat intake in either obese or lean men. However, in obese men UFC was significantly correlated with fat intake from the overall preferred product in the taste test ( r = 0.84, p < 0.05) and with fat intake during the following 24 h. This correlation was lost after RU 486 administration in obese men and was not seen in either condition in lean men. Although RU 486 did not alter fat intake in obese or lean men, correlations between UFC and both measures of fat intake in obese men suggest that cortisol may play a role in the pathophysiology of obesity.

Long distance transport of lambs

Two commercial consignments of 500 lambs were followed from the UK to southern France; one journey lasted 18 h, the other 24 h. Blood samples were taken and measurements were made of liveweight and skin thickness from 100 lambs from each consignment, before and after the journeys. The results from each consignment were very similar, however, interpretation of the results was made difficult by previous commercial handling. The lambs had all been recently bought from local livestock auctions, Increased plasma total protein, plasma albumin, plasma osmolality and skinfold thickness after transportation were indicative of some degree of dehydration. There was a 7% loss in liveweight after both journeys. Measurement of plasma-free fatty acids, betahydroxybutyrate, urea, glucose and cortisol showed that all of these blood constituents were present at more than usual basal levels, both before and after transport. These elevated levels suggested that the lambs' eating patterns had been disrupted before transport and that the lambs were moderately stressed, probably as a consequence of passing through livestock auctions. However, there was no further elevation in levels with transport. The behaviour of the lambs after both journeys indicated that they were all alert and physically fit. They were primarily interested in any food that was available upon arrival and were secondarily interested in drinking, then resting.

Determination of cortisol and associated glucocorticoids in serum and urine by an automated liquid chromatographic assay

We described a method for the determination of urinary free cortisol and glucocorticoids in plasma, used in the diagnosis of adrenal disorders, based on automated reverse-phase high-performance liquid chromatography (HPLC). The within-day and day-to-day CVs were less than 5.5. and 8.0%, respectively. The calibration curves for cortisol and 11-deoxycortisol were linear up to 2000 nmol/L. Cortisol concentrations as low as 3.5 nmol/L in 1 mL of plasma or urine can be measured. Correlation of HPLC results for 40 plasma specimens with those of radioimmunoassay showed r = 0.965. This method is sensitive and free from the interference habitually encountered in immunoassays, and can thus be proposed for research and as a potential reference method.

Hypothalamic-pituitary adrenal function in end-stage non-alcoholic liver disease.

Patients with end-stage liver disease have significant mortality often associated with intercurrent episodes of bleeding or sepsis. Intact adrenal function is essential in such situations. In order to test the hypothesis that adrenal insufficiency might be present in severe liver disease, hypothalamic-pituitary adrenal function was evaluated in patients with end-stage liver disease awaiting transplantation. The study had a prospective, open comparative design with patients restricted to those having non-alcoholic liver disease in order to avoid the confounding direct effects of alcohol on adrenocortical function. Fifty-one consecutive patients with end-stage, non-alcoholic liver disease undergoing evaluation for liver transplantation and 40 healthy controls were studied. Patients who had used corticosteroids (n = 8) or who were unable to complete the investigations (n = 5) were excluded leaving 38 patients eligible for analysis. Adrenal function was evaluated under basal conditions by single morning measurements of plasma total and free cortisol, corticosteroid-binding globulin, dehydroepiandrosterone sulfate and by adrenal stimulation indirectly using insulin-induced (0.1 U/kg, i.v.) hypoglycaemia and/or directly by adrenocorticotrophic hormone (ACTH); 250 micrograms tetracosactrin, i.v.) stimulation. Compared with healthy controls, patients with liver disease had a 64% reduction in maximal increments of plasma cortisol to indirect adrenal stimulation via insulin-induced hypoglycaemia and a 39% reduction to direct adrenal stimulation by ACTH (all P < 0.001). There was a significant negative correlation between the severity of underlying liver disease as assessed by Child-Pugh scores and peak control responses to ACTH (r = -0.647, P < 0.0001) and insulin-induced hypoglycaemia (r = -0.597, P < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Glucocorticoid-induced increase in plasma corticosteroid-binding globulin levels in fetal sheep is associated with increased biosynthesis and alterations in glycosylation.

In fetal sheep, there is a concomitant prepartum rise in cortisol and corticosteroid-binding globulin (CBG) that maintains a low free plasma cortisol level and allows for a low negative feedback effect of cortisol on the secretion of ACTH from the fetal pituitary. However, the stimulus for the prepartum increase in CBG and the mechanism(s) of this effect are not known. It has been proposed that glucocorticoids increase CBG concentrations, and therefore, we infused fetal sheep with the synthetic glucocorticoid dexamethasone (DEX; 2 micrograms/min over 15 min every 2 h for 96 h, n = 5) or saline (n = 5). The plasma corticosteroid-binding capacity increased from 30.0 +/- 2.4 to 55.6 +/- 7.7 and 92.6 +/- 11.1 ng/ml at 48 and 96 h, respectively, of DEX infusion. To examine possible mechanisms of increasing fetal plasma CBG, we first cloned and sequenced a sheep CBG cDNA and purified the protein. This allowed us to deduce the primary structure of ovine CBG and to demonstrate that hepatic CBG mRNA abundance (single transcript of 1.8 kilobases) rose from 0.9 +/- 0.2 to 3.6 +/- 1.6 arbitrary units after 96 h of DEX treatment. Fetal DEX treatment produced a significant increase (7.1 +/- 1.2% to 13.1 +/- 1.4%) in the Concanavalin-A-binding forms of CBG that predominate in adult sheep plasma. There was negligible transfer of purified [125I]CBG from the ewe to fetal plasma, urine, or amniotic fluid. We also injected adult sheep with DEX (10 mg/day for 4 days) and demonstrated a significant decrease in plasma corticosteroid-binding capacity by 24 h, which remained suppressed for the duration of the study. After 96 h of DEX treatment, there was also a significant decrease in adult hepatic CBG mRNA abundance. We conclude that glucocorticoids increase fetal plasma CBG in part by increased hepatic biosynthesis. It may also be accentuated by a change in the glycosylation of CBG, but cannot be attributed to transplacental transfer. Furthermore, glucocorticoid treatment exerts opposite effects on CBG biosynthesis in fetal and adult sheep.

Corticotropin-releasing hormone in baboon pregnancy.

During human pregnancy, plasma CRH immunoreactivity (CRH-IR) rises progressively, peaking during labor and falling after delivery. Among animal species, only higher primates have elevated CRH-IR during pregnancy. This study examines whether changes in plasma CRH-IR in the baboon (Papio hamadryas) are similar to those in the human. CRH-IR was determined by RIA in 16 baboons at different stages of gestation (44 samples) and in 3 males. Assays were performed on Vycor extracts of plasma and CRH-IR diluted in parallel to synthetic human (h) CRH-41 standard. Reverse phase high pressure liquid chromatography and size-exclusion chromatography with Sephadex G-50 showed that baboon CRH-IR eluted in a position similar to that of hCRH-41. Regression analysis revealed a cubic association between plasma CRH-IR and gestational age, with peak concentrations occurring at 60 days gestation (term = 182 days). Although greatly elevated concentrations persisted throughout pregnancy, concentrations in the first half (1-91 days) were significantly higher (mean +/- SEM, 1.9 +/- 0.3 nM/L; n = 27) than in the second half (92-182 days; 1.0 +/- 0.2 nM/L; n = 11; P < 0.003 by t test). CRH-IR fell to low levels by day 1 postpartum. The concentration of total cortisol in nonpregnant animals was 1370.9 +/- 134.9 nM/L (n = 5), which was similar to pregnancy levels (1346.3 +/- 356.1 nM/L; n = 28); there was no gestational age-related pattern evident. Plasma corticosteroid-binding globulin was estimated by RIA, and plasma free cortisol was calculated to be 73 +/- 14 nM/L in pregnant animals and showed no gestational age-related changes. The mean progesterone concentration in the pregnant baboon was 12.5 +/- 2.2 nM/L (7-169 days; n = 27). There was no significant change in progesterone levels during the period of gestation studied; however, they were higher than nonpregnant levels. Baboon and human plasma (0.1 mL each) were incubated with [125I]Tyr-hCRH in Tris-HCl buffer (pH 7.5) and chromatographed with Sephadex G-75, using the same buffer. The radioactivity of fractions was determined, and no CRH-binding protein was identified in baboon plasma. This study indicates that gestational changes in CRH-IR in the baboon are different from those observed in humans. There is a dissociation between maternal plasma CRH and cortisol. The apparent lack of bioactivity of baboon plasma CRH is not due to a circulating binding protein, which is absent in this species.

An Analysis of the Glucagon Response to Hypoglycaemia in Patients with Type 1 Diabetes and in Healthy Subjects

The study aimed to analyse the glucagon response during hypoglycaemia in relation to gender, level of hypoglycaemia, and hyperinsulinaemia as well as its relation to other counterregulatory hormones in patients with Type 1 diabetes and in nondiabetic subjects. Mild hypoglycaemia was induced by an i.v. insulin infusion (244 pmol kg-1h-1) for 180 min in 43 Type 1 diabetic patients and 22 nondiabetic subjects. Venous blood glucose, plasma free insulin, glucagon, adrenaline, noradrenaline, growth hormone, and cortisol were measured every 15-30 min. The hormonal responses during hypoglycaemia were evaluated from the incremental areas under their respective curves. There was a linear correlation between the glucagon response and the decremental area of blood glucose (p < 0.005), but the slope of the regression line in the diabetic group was less steep than in the controls (p < 0.5), and, in spite of the deeper hypoglycaemia in the diabetic groups, their glucagon response was diminished (p < 0.05). Plasma, adrenaline, growth hormone and cortisol all increased during hypoglycaemia. The glucagon response correlated with the responses of growth hormone and cortisol in both groups, while it was positively correlated with the adrenaline response (p < 0.001) and inversely with the plasma insulin (p < 0.001) only in the diabetic patients. Although the insulin infusion rate was identical, the female diabetic patients had a lower metabolic clearance rate of insulin as compared with the males (p < 0.05). There was no statistical difference in the counterregulatory hormone responses between males and females in neither of the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of the percentage of free cortisol in plasma in the dog by ultrafiltration/dialysis

The current methods for measurement of free cortisol are hampered by methodological drawbacks including large sample requirement, length of the procedure, and overestimation or underestimation of free cortisol. We report a technique combining ultrafiltration and dialysis, which could largely overcome these drawbacks, for measurement of the per cent free cortisol in plasma in the dog. This is a modification of the method of Hammond et al. for the determination of sex steroids in man. We found a good positive correlation (r s = 0.87) with equilibrium dialysis, which is considered the golden standard in free cortisol measurements. The 2.5th and 97.5th percentiles of values of free cortisol measured in plasma of 40 healthy household dogs were 5–20 nmol/l or 5.1–11.7% of the total cortisol concentration.

Salivary and plasma cortisol as an index of stress in goats.

Total assayable cortisol in plasma was highly correlated (r = 0.97) with physiologically active free cortisol in plasma after routine management procedures in 1- to 3-weeks-old goats. Transport of adult goats caused significant increases (P less than 0.001) in free cortisol in saliva and in free and total cortisol in plasma. No difference (P greater than 0.05) between concentrations of free cortisol in saliva and in plasma was apparent before or after transport. The results demonstrated that the salivary cortisol method is a useful measure of stress in adult goats, and that the relationship between free and total cortisol in plasma, and the adrenocortical response to transport, appear to be similar in sheep and goats.

Gastric pressure response to low dose dopamine infusion in normal man

The gastric pressure response to distension was measured during intravenous infusion of dopamine at a rate of 2 μg min −1kg −1 over 2h 50min in 5 normal volunteers to determine whether dopamine at this dose potentiated gastric adaptive relaxation, leading to a fall in gastric pressure and thus a potential delay in gastric emptying. This would be of obvious importance in patients being given dopamine at this dose to support renal function and at the same time being fed by nasogastric tube. The pressure response decreased during the first hour in all five subjects (p < 0.01). In 2 it recovered during the third hour to pre-infusion values, but in 2 it remained diminished; in 1 subject the results were equivocal. Circulating dopamine, noradrenaline and adrenaline concentrations all increased during dopamine (p < 0.05), but compared with control there was no difference in plasma free fatty acids, glycerol, cortisol or glucose concentrations. Dopamine at 2 μg min −1 kg −1 produced a transient fall in gastric pressure in all subjects, and a persistent fall in some. The changes in gastric pressures were seen at infusion rates that produced no metabolic or inotropic effects.

Changes in injection-site blood flow and plasma free insulin concentrations in response to stress in type 1 diabetic patients.

In order to test the effect of stress on injection-site blood flow and blood glucose control, 16 C-peptide negative patients were studied on a stress day, when a 30-min Stroop Colour-Word Test was completed, and a control day, when a cartoon was shown. Unmodified insulin was injected subcutaneously into the thigh before the test, and injection-site blood flow measured throughout the experiment with a thermal clearance probe. Blood glucose and plasma free insulin, glucagon, growth hormone, cortisol, and catecholamines were measured at intervals before, during, and after stress. Patients showed a significant overall rise in injection-site blood flow with the Stroop test from 4.1 (SD 1.6) to 5.2 (1.8) ml 100-g-1 min-1 (increase 38.1 (37.8) %, p less than 0.001). There was no overall significant difference between stress and control days in blood glucose or plasma free insulin levels, with differences in mean blood glucose levels during stress between the 2 days varying from -4.2 mmol l-1 to +6.3 mmol l-1 in individual patients. The increase in injection-site blood flow with stress correlated significantly with the increase in plasma free insulin concentration both during (r = 0.55) and after stress (r = 0.71). Differences in blood glucose concentration between stress and control day for each patient showed strong correlation with differences in plasma free insulin both during (r = -0.73) and after stress (r = -0.79). Differences in counter-regulatory hormones occurred but correlated poorly with blood glucose difference. Thus, stress affects the blood flow at the injection site, and this in turn affects insulin absorption. Most of the blood glucose response to stress is explained by changes in free insulin concentration.

Cushing's syndrome associated with ectopic corticotropin production and small-cell lung cancer.

This study was undertaken to review the clinical and laboratory features and response to treatment of patients with Cushing's syndrome associated with ectopic corticotropin (adrenocorticotropic hormone; ACTH) production and small-cell lung cancer (SCLC). We undertook a retrospective chart review of 545 patients with SCLC seen at Toronto General Hospital between 1980 and 1990 and identified 23 patients (4.5%) with Cushing's syndrome and ectopic ACTH production. There were 17 male and six female patients, with a median age of 60 years. The syndrome was diagnosed at the time of initial presentation of SCLC in 13 patients and at relapse in 10 patients. Seven patients had limited disease and 16 had extensive disease at their initial diagnosis of SCLC, but 20 of 23 had extensive disease at the time of diagnosis of Cushing's syndrome. Ten patients had bone marrow involvement. The most frequent physical findings included edema (83%) and proximal myopathy (61%). All patients had elevated plasma and urinary free cortisol levels; 22 had a hypokalemic alkalosis, and 13 had hyperglycemia. Only one patient had a normal ACTH level. The response rate (complete plus partial) to chemotherapy for patients who had the syndrome diagnosed at initial presentation of SCLC was only 46%, and their median survival was only 3.57 months. Only two patients achieved complete normalization of all hormone parameters, and neither experienced hormone relapse at the time of SCLC relapse. Complications of therapy included gastrointestinal (GI) ulceration (six patients), GI bleeding (four), perforation of a duodenal ulcer (one), pneumonia (10), septic shock (three), and fungal infections (five). Ectopic ACTH production is associated with a low response to chemotherapy, short survival, and a high rate of complication to therapy.

Hormonal responses to ingesting water or a carbohydrate beverage during a 2 h run

Ingestion of fluids providing carbohydrate and electrolytes extends endurance times during prolonged exercise. To understand the contribution of these factors, we examined hormonal, physiologic, and metabolic responses to ingesting water (W) or a 7% glucose polymer/fructose/electrolyte solution (GPFE) in 10 men (age: 30 +/- 2 yr, VO2max: 57.4 +/- 3.2 ml.kg-1.min-1) who ran on a treadmill for 2 h at 60-65% of their VO2max. Subjects drank 200 ml of W or GPFE at 0-time and every 30 min while running (30,60, and 90 min). Changes in serum sodium, potassium, and osmolality; heart rate; plasma lactate and glucose; and serum insulin and plasma norepinephrine were similar for both fluid treatments. In contrast, changes in serum free fatty acids (FFA), plasma cortisol, and arginine vasopressin (AVP) differed across fluid treatments: with GPFE, exercise abolished the rise in plasma cortisol, and attenuated the rise in both AVP and FFA. The observed suppression of cortisol and AVP was not related to changes in any of the parameters examined, but were strongly correlated with each other. These findings suggest that adding carbohydrate and electrolytes to fluids ingested during prolonged exercise decreases activation of the hypothalamic-pituitary-adrenal axis, a potentially beneficial change. However, mobilization of FFA was also decreased. The mechanism by which they occur remains elusive.

Evidence for Impaired Activation of the Hypothalamic-Pituitary-Adrenal Axis in Patients with Chronic Fatigue Syndrome

Chronic fatigue syndrome is characterized by persistent or relapsing debilitating fatigue for at least 6 months in the absence of a medical diagnosis that would explain the clinical presentation. Because primary glucocorticoid deficiency states and affective disorders putatively associated with a deficiency of the arousal-producing neuropeptide CRH can be associated with similar symptoms, we report here a study of the functional integrity of the various components of the hypothalamic-pituitary-adrenal axis in patients meeting research case criteria for chronic fatigue syndrome. Thirty patients and 72 normal volunteers were studied. Basal activity of the hypothalamic-pituitary-adrenal axis was estimated by determinations of 24-h urinary free cortisol-excretion, evening basal plasma total and free cortisol concentrations, and the cortisol binding globulin-binding capacity. The adrenal cortex was evaluated indirectly by cortisol responses during ovine CRH (oCRH) stimulation testing and directly by cortisol responses to graded submaximal doses of ACTH. Plasma ACTH and cortisol responses to oCRH were employed as a direct measure of the functional integrity of the pituitary corticotroph cell. Central CRH secretion was assessed by measuring its level in cerebrospinal fluid. Compared to normal subjects, patients demonstrated significantly reduced basal evening glucocorticoid levels (89.0 +/- 8.7 vs. 148.4 +/- 20.3 nmol/L; P less than 0.01) and low 24-h urinary free cortisol excretion (122.7 +/- 8.9 vs. 203.1 +/- 10.7 nmol/24 h; P less than 0.0002), but elevated basal evening ACTH concentrations. There was increased adrenocortical sensitivity to ACTH, but a reduced maximal response [F(3.26, 65.16) = 5.50; P = 0.0015). Patients showed attenuated net integrated ACTH responses to oCRH (128.0 +/- 26.4 vs. 225.4 +/- 34.5 pmol/L.min, P less than 0.04). Cerebrospinal fluid CRH levels in patients were no different from control values (8.4 +/- 0.6 vs. 7.7 +/- 0.5 pmol/L; P = NS). Although we cannot definitively account for the etiology of the mild glucocorticoid deficiency seen in chronic fatigue syndrome patients, the enhanced adrenocortical sensitivity to exogenous ACTH and blunted ACTH responses to oCRH are incompatible with a primary adrenal insufficiency. A pituitary source is also unlikely, since basal evening plasma ACTH concentrations were elevated. Hence, the data are most compatible with a mild central adrenal insufficiency secondary to either a deficiency of CRH or some other central stimulus to the pituitary-adrenal axis. Whether a mild glucocorticoid deficiency or a putative deficiency of an arousal-producing neuropeptide such as CRH is related to the clinical symptomatology of the chronic fatigue syndrome remains to be determined.

The welfare of pigs in two farrowing/lactation environments: cortisol responses of sows

Plasma free cortisol concentrations were measured in 24 primiparous sows housed from Day 104 after mating up to Day 2 after parturition. Concentrations were measured in 22 of these sows, from Days 2–29 of lactation, housed in either commercial farrowing crates (Crate treatment) or farrowing pens with straw added (Pen treatment). The mortality and growth data of litters from the time of birth to weaning were also recorded. The mean plasma free cortisol concentration was higher in sows housed in the Crate treatment, compared with sows housed in the Pen treatment, on the first day of treatment (8.2 and 5.8 nmol l −1, respectively, P < 0.05) and on Day 28 of lactation (5.6 and 4.0 nmol l −1, respectively, P < 0.05). The data suggest that housing treatment around parturition and during lactation may have only limited effects on the welfare of sows, providing that lactation is no longer than 28 days. On Days 21 and 24, there were no effects of treatment on free cortisol concentrations and no response to the exogenous adrenocorticotrophic hormone (ACTH), respectively. However, on Day 28, there were mean increases in the concentrations of free cortisol of approximately 150% and approximately 60%, respectively; these may have been the result of unavoidable attention of the piglets to the sows.

Serum and Saliva Cortisol Responses and Blood Lactate Accumulation during Incremental Exercise Testing

In six male physically active subjects the adrenocortical and metabolic changes in response to incremental exercise testing were investigated. Blood and saliva samples were taken at rest, at the end of every workload (duration 4 min with 50 W increment), immediately and 10 min after 1 min all out spurt on the electrically braked cycle ergometer. Both saliva and serum cortisol were measured as well as blood lactate. The cortisol response in serum and in saliva showed similar dynamics (r = 0.86, p less than 0.001, n = 50) at submaximal work. At maximal work the serum cortisol concentration showed a transitory decrease, which was not manifested in saliva. It is hypothesized that a factor related to the metabolic acidosis masks the actual adrenocortical response in the serum but not in saliva. Correlation analysis revealed a positive relation between lactate and cortisol in serum (r = 0.56, p less than 0.01, n = 50) and saliva (r = 0.70, p less than 0.01, n = 50). Apparently, salivary cortisol closely reflects plasma free cortisol level, presenting advantage over total cortisol measurements. Moreover salivary measurement will permit studies in their authentic settings and should assist attempts to understand the nature of the adrenocortical function in exercise.