Potentiation of the ACTH response to metyrapone by L-dopa in the monkey.

The intravenous injection of L-Dopa (15 mg/kg) to monkeys (Macaca mulatta) failed to alter plasma concentrations of ACTH and of 11-deoxy-cortisol. When cortisol synthesis was blocked with iv metyrapone, potentiation of ACTH secretion by L-Dopa became apparent. Simultaneous injection of L-Dopa and metyrapone resulted in a marked increase in plasma ACTH from 93 +/- 18 pg/ml to 432 +/- 80 pg/ml, whereas plasma 11-deoxycortisol increased from 1.5 +/- 0.2 mug/100 ml to 14.6 +/- 1.0 mug/100 ml 90 min after treatment. Throughout the experiment the rise in ACTH and in 11-deoxycortisol following coadministration of L-Dopa and metyrapone was significantly (P less than 0.01) higher than that produced by metyrapone administration alone. The results suggest that acute administration of L-Dopa in monkeys enhances the response of ACTH to metyrapone. L-Dopa (or one of its metabolites) probably acts upon a noradrenergic or a dopaminergic system located in the hypothalamus to alter the release of hypothalamic corticotropin regulatory factor(s) and thereby enhance the release of ACTH.     

Effect of an antiserotoninergic drug, metergoline, on the ACTH and cortisol response to insulin hypoglycemia and lysine-vasopressin in man.

The effect of metergoline, a specific antiserotoninergic drug, on ACTH secretion was investigated in 29 normal volunteers and in 4 patients with increased ACTH production (3 with Addison's disease, 1 with Cushing's disease). In 15 normal subjects, a 4-day treatment with 10 mg daily of metergoline significantly blunted the ACTH response to insulin hypoglycemia. Mean peak ACTH values before and after treatment were, respectively, 333 +/- 39.2 (SE) and 235 +/- 38.8 pg/ml (P less than 0.05). The corresponding values of plasma cortisol were 29.6 +/- 2.96 and 20.5 +/- 2.67 mug/100 ml (P less than 0.05). In contrast, metergoline failed to affect the ACTH response to lysine-vasopressin (LVP) administered iv (8 subjects studied) and im (6 subjects studied). In 3 patients suffering from Addison's disease, an appreciable although not statistically significant lowering of the plasma ACTH levels was noted during metergoline administration. The mean pre- and post-treatment values of plasma ACTH in these patients were, respectively, 1116 +/- 192.2 and 666 +/- 100.8 pg/ml, 4240 +/- 50.0 and 3398 +/- 368.0 pg/ml, and 431 +/- 44.0 and 352 +/- 23.9 pg/ml. In one patient with Cushing's disease caused by a pituitary adenoma, metergoline did not appreciably modify plasma ACTH levels. Taken together, these results lend support to the concept of a physiological stimulating effect of serotonin on ACTH secretion. Moreover, they are compatible with the view that serotonin exerts its action chiefly at the hypothalamic level while LVP promotes ACTH release by a primary action on the pituitary.     

Plasma adrenocorticotropin, cortisol, and aldosterone responses to corticotropin-releasing factor: modulatory effect of basal cortisol levels

Two hundred micrograms of corticotropin-releasing factor (CRF) were administered as an iv bolus injection to 10 normal subjects (5 men and 5 women). Mean plasma ACTH levels rose significantly (P less than 0.0005, by Friedman's nonparametric analysis of variance) from a basal value of 27 +/- 5 pg/ml (mean +/- SEM) to a peak value of 63 +/- 8 pg/ml 30 min after CRF administration. This ACTH response was followed by a rise in plasma mean cortisol levels (P less than 0.0005, by Friedman's test) from a baseline value of 12.3 +/- 1.4 micrograms/100 ml to a peak value of 21.0 +/- 0.7 micrograms/100 ml 60 min after CRF and a rise in mean plasma aldosterone levels from a basal value of 13 +/- 2 ng/100 ml to a peak value of 23 +/- 2 ng/100 ml. There was no significant difference between men and women in the responsiveness of ACTH, cortisol, and aldosterone to CRF administration. The individual basal cortisol levels were highly significantly and negatively correlated with the areas under the individual ACTH curves (r = -0.76; P less than 0.005, by Pearson's correlation test) and cortisol curves (r = -0.91; P less than 0.001, by Pearson's test). These data suggest a modulatory effect of physiological cortisol levels on the response of the pituitary-adrenal axis to CRF.     

Effects of the opiate agonist loperamide on pituitary-adrenal function in patients with suspected hypercortisolism

In the present work the possible use of loperamide, an opiate agonist, in the dynamic evaluation of patients with suspected hypercortisolism was investigated. The effects of loperamide on plasma ACTH and cortisol levels were evaluated in normal subjects and in 58 patients with suspected Cushing's syndrome. The results were compared to those obtained after the overnight dexamethasone suppression test. In normal subjects plasma ACTH and cortisol levels were significantly (p less than 0.005) suppressed by both loperamide (16 mg po) and dexamethasone (1 mg po). In 17 patients, in whom the diagnosis of Cushing's syndrome was confirmed by subsequent investigations, neither loperamide or dexamethasone inhibited cortisol (from a baseline of 606 +/- 55 nmol/L) to a nadir of 502 +/- 43 nmol/L and 539 +/- 50 nmol/L, respectively) and ACTH concentration (from a basal level of 70.1 +/- 11.8 pg/ml to a nadir of 46.0 +/- 8.6 pg/ml and 54.3 +/- 7.5 pg/ml, respectively). In 34 patients, in whom the suspect of hypercortisolism was ruled out, either loperamide or dexamethasone suppressed the pituitary-adrenal axis: cortisol and ACTH levels significantly fell from 417 +/- 24 nmol/L and 28.3 +/- 3.5 pg/ml to 60 +/- 6 nmol/L and 14.4 +/- 1.4 pg/ml after loperamide and to 26 +/- 4 nmol and 16.4 +/- 1.7 pg/ml after dexamethasone. In 7 patients discordant responses were observed. In 3 patients treated with antiepileptic drugs ACTH and cortisol levels were inhibited by loperamide, but not by dexamethasone.(ABSTRACT TRUNCATED AT 250 WORDS)     

DIFFERENTIAL EFFECTS OF OVINE AND HUMAN CORTICOTROPHIN-RELEASING FACTOR IN HUMAN SUBJECTS

Ten healthy subjects received 200 micrograms of human CRF (hCRF) and 200 micrograms of ovine CRF (oCRF) as an intravenous bolus injection on two different occasions. After hCRF plasma ACTH levels rose significantly (P less than 0.0005, by Friedman's nonparametric analysis of variance) from a basal value of 35 +/- 3 pg/ml (mean +/- SEM) to a peak value of 80 +/- 7 pg/ml 30 min after hCRF administration. This ACTH response was followed by a rise in plasma cortisol levels (P less than 0.0005, by Friedman's test) from a baseline value of 0.32 +/- 0.03 mumol/l to a peak value of 0.56 +/- 0.02 mumol/l 60 min after hCRF. Ovine CRF elicited similar rises in the plasma ACTH and cortisol levels. However, as derived from the faster rate of decline of ACTH and cortisol after hCRF than after oCRF, human CRF had a significantly shorter duration of action than ovine CRF in humans. Human CRF not only stimulated ACTH release by the human pituitary gland but also prolactin release. After hCRF administration prolactin levels rose significantly (P less than 0.005, by Friedman's test) from a basal value of 179 +/- 18 mU/l to a peak value of 288 +/- 34 mU/l at 10 min.     

RECOVERY FROM GLUCOCORTICOID INHIBITION OF THE RESPONSES TO CORTICOTROPHIN-RELEASING HORMONE

We have characterized the recovery of the hypothalamic-pituitary-adrenal (HPA) axis from inhibition by short-term prednisolone administration. Prednisolone was given in a dosage averaging 25 mg at 12 h intervals orally for up to 2 weeks to adult volunteers. Human corticotrophin releasing hormone (hCRH) tests were performed at 0901 h using a bolus injection of 1 microgram/kg before and 24-48 h after discontinuing the prednisolone. In the initial control study, hCRH stimulated a two-fold rise in plasma ACTH and a 30% rise in plasma cortisol within 30 min (ACTH rose from 18.5 +/- 4.5, SEM, pg/ml to 36.5 +/- 12.6 pg/ml and cortisol from 415 +/- 58 to 531 +/- 69 nmol/l in response to hCRH. One dose of prednisolone had no effect on the ACTH or cortisol response to hCRH administered 24 h later. Twenty-four hours after discontinuing a 1 week course of prednisolone, baseline plasma ACTH (3.9 +/- 0.6 pg/ml) and cortisol (146 +/- 17 nmol/l) were markedly suppressed, as was the cortisol response to hCRH (peak 198 +/- 22). However, the plasma ACTH response to hCRH was not significantly suppressed. Forty-eight hours after discontinuing prednisolone, the recovery of ACTH secretion was complete (baseline 10.9 +/- 4.2, peak 36.4 +/- 14.8 pg/ml), but the cortisol response to hCRH was still depressed (peak 294 +/- 66 nmol/l). Recovery from a 2 week course of prednisolone had similar characteristics except plasma cortisol was depressed more profoundly. Plasma dehydroepiandrosterone (DHA) during hCRH tests and dehydroepiandrosterone sulphate (DHAS) paralleled plasma cortisol.(ABSTRACT TRUNCATED AT 250 WORDS)     

Is the plasma ACTH concentration a reliable parameter in the insulin tolerance test?

OBJECTIVE: The insulin tolerance test (ITT) is an established standardized test for the evaluation of the hypothalamic-pituitary-adrenal axis. While a peak cortisol value of >18 microg/dl is usually interpreted as a sufficient response to the ITT, the plasma ACTH response has not yet been standardized. METHODS: We evaluated retrospectively the peak plasma ACTH concentrations during 140 ITTs in 125 patients with suspected pituitary insufficiency and prospectively in 15 healthy subjects. RESULTS: All healthy subjects had a peak cortisol concentration >/=18 microg/dl; 32 of 125 tests in the patients showed an insufficient cortisol response (peak cortisol concentration <18 microg/dl). The peak stimulated ACTH concentration in patients with secondary adrenal insufficiency (SAI) was 49.2+/-37.2 pg/ml (mean+/-s.d.) vs 130.9+/-89.3 pg/ml in patients without SAI, and 110.9+/-55.4 pg/ml in normal subjects (P<0.001). There was a weak, but significantly positive correlation between the peak ACTH and peak cortisol concentrations (rho=0.446, P<0.001), but there was also a very wide spread of the values. Defining a cut-off value for the peak plasma ACTH concentration with a sufficient sensitivity and specificity to identify patients with an impaired hypothalamic-pituitary-adrenal (HPA) axis was not possible. A peak plasma ACTH <20 pg/ml as a cut-off value had a sensitivity of 25% and a specificity of 98% for SAI. A cut-off value of a peak plasma ACTH <140 pg/ml had a sensitivity of 97% but a low specificity of 39%. CONCLUSIONS: Although there is a significant positive correlation between the peak ACTH and the peak cortisol concentrations, we conclude that there is no additional benefit in determining the ACTH concentrations during an ITT. Because of the strong variations of the values, the peak ACTH concentration is a poor parameter for the evaluation of the HPA axis.     

FK 33-824, a met-enkephalin analog, blocks corticotropin-releasing hormone-induced adrenocorticotropin secretion in normal subjects but not in patients with Cushing's disease

To further elucidate the site of action of opioids on the pituitary-adrenal axis, we studied the effect of D-Ala2,MePhe4,met-(O)enkephalin-ol (Sandoz, FK 33-824) on plasma ACTH and beta-endorphin immunoreactivity and serum cortisol in 7 normal subjects and 11 patients with Cushing's syndrome (Cushing's disease, n = 7; adrenal adenoma, n = 2; ectopic Cushing's syndrome, n = 2) after administration of human corticotropin-releasing hormone (hCRH). hCRH (0.1 mg; Bachem) was injected iv after pretreatment with 0.5 mg FK 33-824, im, or 0.9% saline. In normal subjects, the hCRH-induced ACTH, beta-endorphin, and cortisol increases were almost completely abolished by pretreatment with FK 33-824. Mean peak (+/- SEM) hormone concentrations were significantly reduced (ACTH, 16.7 +/- 3.5 vs. 45.3 +/- 7.8 pg/ml; beta-endorphin, 151 +/- 25 vs. 277 +/- 51 pg/ml; cortisol, 8.1 +/- 1.2 vs. 19.5 +/- 2.6 micrograms/dl; P less than 0.02), as were secretory areas (P less than 0.02). These results indicate a direct pituitary action of the synthetic met-enkephalin. In contrast, in patients with Cushing's disease, FK 33-824 did not inhibit hCRH-induced hormone release. Instead, maximum ACTH and beta-endorphin concentrations were slightly but not significantly higher after the administration of FK 33-824 (ACTH, 292 +/- 143 vs. 131 +/- 32 pg/ml; beta-endorphin, 2409 +/- 763 vs. 1921 +/- 600 pg/ml). These findings indicate a defect in inhibitory opiodergic control of ACTH secretion in patients with Cushing's disease, which may contribute to the pathological ACTH hypersecretion. In patients with Cushing's syndrome due to an adrenal adenoma or ectopic ACTH secretion, neither hCRH nor FK 33-824 altered hormone concentrations.     

Adrenocortical function in a prototherian mammal, Tachyglossus aculeatus (Shaw).

The peripheral plasma concentrations and production rates of corticosterone and cortisol were measured in the conscious, unrestrained echidna (Tachyglossus aculeatus) under basal conditions and during maximal ACTH stimulation. Using Sephadex LH-20 column chromatography and radioligand assay, only cortisol and corticosterone could be detected in the peripheral blood plasma at very low concentrations of 0-07 +/- 0-03 (S.E.M.) mug/100 ml and 0-14 +/- 0-07 mug/100 ml respectively. Two-hourly sampling over periods of 36-48 h disclosed a diurnal periodicity in the combined plasma concentration of these corticosteroids, the high concentrations corresponding to periods of behavioural activity. Marked, short-term fluctuations in plasma corticosteroid concentration were also observed during periods of more frequent (20 min) sampling. Constant rate i.v. infusion of synthetic ACTH increased the plasma concentrations of both steroids to maximal values of 0-42 +/- 0-23 mug cortisol/100 ml and 1-06 +/- 0-56 mug corticosterone/100 ml at infusion rates of 1 i.u. ACTH/kg/h. This is approximately 1/160 of the potency of this ACTH in man. The production rates of corticosterone and cortisol, measured by isotope dilution during constant rate i.v. infusion of 3H-labelled tracers, were only 0-35 +/- 0-21 and 0-56 +/- 0-26 mug/kg/h respectively during saline infusion, and increased to 2-86 +/- 3-47 and 2-74 +/- 2-07 mug/kg/h during the infusion of 1 i.u. ACTH/kg/h. The metabolic clearance rate of cortisol was greater than that of corticosterone and both were depressed by ACTH. Plasma corticosteroid concentrations were increased after surgery during ether anaesthesia and in sick animals with heavy worm infestation. It is concluded that the adrenal cortex of echidnas responds to ACTH stimulation and stress in a similar way to eutherians, but the level of activity is much lower.     

A simple and rapid method to measure non-protein-bound fractions of cortisol, testosterone and oestradiol by equilibrium dialysis: comparison with centrifugal filtration.

A simple method for measuring the free, non-protein-bound steroid fraction in plasma by equilibrium dialysis is described. The alteration occurring in the volume of the inner phase (undiluted plasma) is corrected by the difference in weight before and after dialysis. Total cortisol was determined by radioimmunoassay. Although it is not possible to differentiate between values for total cortisol after ACTH stimulation (242.2+/-shing's syndrome (n: 15)), and women treated with oestrogens (211.8+/-42.0 ng/ml (n: 20)), there were significant differences for free cortisol (ACTH stimulation: 29.3+/-5.6 ng/ml; Cushing's syndrome: 31.5+/-8.6 ng/ml; women under increased oestrogenic activity: 10.0+/-2.1 ng/ml; pregnant women: 13.7+/-5.1 ng/ml plasma). Compared with normal values for healthy women and men (9.3+/-1.4 ng/ml), women with increased oestrogenic activity showed slight elevations of free cortisol. Compared to cortisol, the percentage of dialysable testosterone and oestradiol was lower in women than in men (1.57 vs. 2.08% for testosterone and 1.68 vs. 2.15% for oestradiol). In healthy men the concentration of free steroid was 13.1+/-1.0 ng free testosterone/100 ml plasma (0.44+/-0.045 pg free oestradiol/ml plasma), in healthy women 0.64+/-0.07 ng/100 ml (0.98+/-0.10 pg/ml) and in women receiving oestrogens 0.37+/-0.04 ng/100 ml (0.01+/-0.015 pg/ml). When the method described here for determing the free fractions of cortisol (n: 45), oestradiol (n: 18) and testosterone (n: 18) at 37 degrees C is compared with the method of centrifugal filtration, the correlation was r: 0.80 r: 0.86 and r: 0.91, respectively. In practice, equilibrium dialysis with undiluted plasma is simple, fast and can be applied to all steroid hormones. It allows direct measurements of non-protein-bound steroids under nearly physiological conditions.     

Sodium salicylate augments the plasma adrenocorticotropin and cortisol responses to insulin hypoglycemia in man

To test the hypothesis that prostaglandins attenuate neuroendocrine responses to changes in circulating glucose levels in man, we studied the effects of sodium salicylate (SS), a prostaglandin synthesis inhibitor, on the plasma ACTH and cortisol responses to insulin hypoglycemia. Six normal men were given insulin (0.05 U/kg, iv) on 2 different days during the infusion of either SS (40 mg/min) or saline. Compared to the saline control, SS had no significant effect on either the rate of fall of plasma glucose after insulin or the glucose nadir (mean +/- SEM, 33 +/- 3 vs. 36 +/- 3 mg/dl; P = NS). Peak ACTH levels after insulin were higher during SS compared to those during saline in all six subjects (316 +/- 95 vs. 102 +/- 26 pg/ml; P less than 0.05), and SS had a clear effect to increase both the overall ACTH response (F = 21.3; P less than 0.01, by analysis of variance) and the plasma cortisol response (F = 6.72; P less than 0.05, by analysis of variance). The most striking example of this effect of SS occurred in one subject whose peak plasma ACTH was only 44 pg/ml during saline but reached 750 pg/ml during SS despite an identical fall of plasma glucose to 42 mg/dl. Augmentation of the ACTH and cortisol responses to insulin hypoglycemia may be the result of an alteration by SS of recognition of glucose levels by glucose-sensitive cells of the brain, and effect which could be due to the inhibition of prostaglandin synthesis.     

Evidence that cortisol inhibits basal adrenocorticotropin secretion in the sheep fetus by 0.70 gestation

To ascertain if reductions in fetal plasma cortisol cause increases in fetal plasma ACTH, we treated pregnant ewes or their fetuses with aminoglutethimide (10 mg/kg BW) and metyrapone (20 mg/kg BW) and measured the hormonal responses with RIAs. When given to fetuses (n = 9) at 0.90 +/- 0.01 gestation (term-145 days), the steroid synthesis inhibitors reduced fetal plasma cortisol from 35.1 +/- 11.9 to 18.5 +/- 6.2 ng/ml (P less than 0.01) and plasma ACTH increased from 37 +/- 7 to 189 +/- 74 pg/ml (P less than 0.02). Thus, late in gestation cortisol from the fetal adrenal suppresses basal fetal ACTH secretion. Blockade of steroid biosynthesis in pregnant ewes carrying intact fetuses at 0.76 +/- 0.02 gestation (n = 11) or adrenalectomized fetuses at 0.81 +/- 0.01 gestation (n = 6) also reduced cortisol and increased ACTH in fetal plasma. In intact fetuses cortisol declined from 9.4 +/- 2.0 to 3.6 +/- 0.9 ng/ml (P less than 0.05), and ACTH increased from 46 +/- 8 to 183 +/- 67 (P less than 0.01); cortisol declined in adrenalectomized fetuses from 2.1 +/- 0.4 to 1.1 +/- 0.3 ng/ml (P less than 0.01), and ACTH increased from 106 +/- 13 to 400 +/- 104 pg/ml (P less than 0.01). Cortisol infusions into intact and adrenalectomized fetuses prevented both the decline in steroid concentration caused by the biosynthesis inhibitors given to the ewe and the increase in fetal plasma ACTH concentration. These data indicate that reductions in plasma cortisol in adrenalectomized fetuses or intact fetuses at a time in development when the fetal adrenal produces little cortisol cause compensatory increases in fetal plasma ACTH concentration. The simplest explanation for these observations is that from approximately 0.70 gestation, basal fetal ACTH secretion is tonically inhibited by cortisol circulating in fetal plasma. This cortisol can originate from sources other than the fetal adrenal.     

The relationship of saline-induced changes in vasopressin secretion to basal and corticotropin-releasing hormone-stimulated adrenocorticotropin and cortisol secretion in man

To investigate the effect of endogenous arginine vasopressin (AVP) on ACTH secretion, normal subjects were given infusions of either hypertonic saline (HS) or isotonic saline (NS) combined with human corticotropin-releasing hormone (CRH) or placebo. Basal plasma AVP was 2.3 +/- 0.3 (+/- SE) pg/ml, did not change with NS treatment, and rose to 5.4 +/- 0.6 pg/ml during HS infusion (P less than 0.01). Both basal and CRH-stimulated plasma ACTH and cortisol concentrations increased during HS infusion. Peak plasma ACTH and cortisol levels were 11.4 +/- 1.5 pg/ml and 8.6 +/- 0.8 micrograms/dl, respectively, during the HS (plus placebo) infusion. During the NS (plus placebo) infusion, plasma ACTH and cortisol gradually declined to 6.8 +/- 0.5 pg/ml and 2.6 +/- 0.4 micrograms/dl. The timing of the rise in ACTH during the HS infusion paralleled the rise in AVP. When an iv dose of 1 microgram/kg CRH was administered during the saline infusions, peak plasma ACTH and cortisol levels were 27.7 +/- 6.3 pg/ml and 17.5 +/- 1.0 micrograms/dl, respectively, during the HS infusion and 15.6 +/- 1.7 pg/ml and 13.4 +/- 1.2 micrograms/dl during the NS infusion. When the areas under the hormone response curves were compared, CRH stimulated ACTH and cortisol secretion to a greater extent than did HS (P less than 0.05). The hormonal stimulation due to combined CRH and hypertonic saline was greater than that attributable to either factor alone (P less than 0.025), but was not different than the sum of the effects of the individual factors. These results indicate that increases in endogenous AVP produced by HS are associated with increases in both basal and CRH-stimulated ACTH and cortisol release. The effect of HS appears to be additive to but not consistently synergistic with the effect of CRH.     

THE EFFECT OF CHOLINERGIC BLOCKADE ON THE ACTH, β-ENDORPHIN AND CORTISOL RESPONSES TO INSULIN-INDUCED HYPOGLYCAEMIA

To assess the effect of cholinergic blockade on the ACTH, beta-endorphin and cortisol responses to insulin-induced hypoglycaemia, six healthy male volunteers each underwent two insulin tolerance tests in random order, separated by at least 1 week with and without atropine. ACTH levels were significantly greater at +45 min (mean +/- SEM, 223 +/- 21 pg/ml vs 148 +/- 15 pg/ml, P less than 0.01) and at +120 min (54 +/- 11 pg/ml vs 29 +/- 10 pg/ml, P less than 0.05). beta-endorphin levels were significantly greater at +30 min (170 +/- 45 pg/ml vs 96 +/- 32 pg/ml, P less than 0.05) and at +105 min (81 +/- 14 pg/ml vs 54 +/- 7 pg/ml, P less than 0.01). Cholinergic blockade had no effect on plasma glucose or cortisol concentrations. This study demonstrates that cholinergic blockade with atropine facilitates the ACTH and beta-endorphin responses to insulin-induced hypoglycaemia without altering the cortisol responses.     

Inhibition of ACTH response to oral and intravenous metyrapone by antiserotoninergic treatment in man.

Plasma ACTH levels after oral and iv metyrapone administration were studied in 7 and 5 healthy women respectively both under basal conditions and after a 4-day treatment with metergoline, a specific antiserotoninergic agent. In 3 additional women, the effects of methysergide, another antiserotoninergic drug, on the plasma ACTH rise induced by oral metyrapone, were evaluated. A significant lowering of the plasma ACTH levels attained after either oral or iv metyrapone was observed following metergoline administration: 149+/-64.3 vs 239+/-49.1 pg/ml (mean peak values), P less than 0.05 in the oral test and 331+/-19.7 vs 221+/-19.5 pg/ml, P less than 0.02 in the iv test. The fall of plasma cortisol caused by metyrapone was comparable before and after the antiserotoninergic treatment. An interference of metergoline in the ACTH radioimmunoassay was also excluded. After metergoline administration, a slight reduction in the baseline plasma ACTH values was noted: 79+/-7.7 vs 67+/-7.7 pg/ml (NS). A decrease, however not statistically significant, of the metyrapone-induced plasma ACTH elevation occured after methysergide administration: 421+/-150.7 vs 344+/-135.1 pg/ml. These results can be interpreted as indicating that antiserotoninergic treatment caused an inhibition of hypophysial ACTH release in response to metyrapone. Caution is recommended, however, before concluding, on the basis of these findings, that serotonin as such plays a physiological stimulating role on ACTH secretion.     

Responsivity of adrenocorticotropin to corticotropin-releasing hormone and lack of suppressibility by dexamethasone are related phenomena in Cushing's disease

The ACTH and cortisol responses to 100 micrograms ovine corticotropin-releasing hormone (CRH) in 19 consecutive patients with Cushing's disease were compared with those in 13 normal subjects. In 2 patients with Cushing's disease, plasma ACTH and cortisol did not increase after CRH administration. Compared to the normal subjects, maximal ACTH increments [135 +/- 25 (+/- SEM) vs. 42 +/- 6 pg/ml; P less than 0.001, by Wilcoxon's two-sample test] and maximal cortisol increments (17.7 +/- 1.8 vs. 9.4 +/- 1.1 micrograms/100 ml; P less than 0.01 by Wilcoxon's test) after CRH were significantly higher in the 17 CRH-responsive patients with Cushing's disease. In the normal subjects, there was a significant negative correlation between the basal cortisol level and the maximal ACTH (r = -0.65; P less than 0.05, by Spearman's rank correlation test) and cortisol (r = -0.95; P less than 0.001, by Spearman's test) responses to CRH. In contrast, in the CRH-responsive Cushing patients, there was no significant correlation between the basal cortisol level and the maximal ACTH (r = 0.10; P greater than 0.10, by Spearman's test) and cortisol (r = 0.14; P greater than 0.10, by Spearman's test) increments after CRH treatment. In the normal subjects, there was no significant correlation between the basal ACTH level and the maximal ACTH increments after CRH administration (r = -0.24; P greater than 0.10, by Spearman's test). Again in contrast, in the CRH-responsive Cushing patients, maximal ACTH increments after CRH treatment correlated positively with basal ACTH levels (r = 0.69; P less than 0.005, by Spearman's test). Moreover, in these patients, the maximal ACTH increments after CRH were positively correlated with the ACTH levels after suppression with higher and lower doses of dexamethasone. We conclude that in Cushing's disease, unlike in normal subjects, circulating cortisol is not the major modulator of ACTH and cortisol responses to CRH, and that in these patients, responsivity of ACTH to CRH and lack of suppressibility by dexamethasone are related phenomena.     

Distribution of plasma glucagon immunoreactivity in a patient with suspected glucagonoma.

Gel filtration of plasma from a patient with a clinical syndrome of glucagonoma and a total plasma glucagon level of 2600 pg/ml, revealed the four glucagon immunoreactive fractions found in normal subjects. The total hyperglucagonemia observed was due to high levels of true glucagon and proglucagon moieties. The so-called "big plasma glucagon" (BPG) measured 190 pg/ml (normal average 113 +/- 79 pg/ml, Mean +/- SD, N = 10); the large glucagon immunoreactivity, LGI (9000 mol wt), measured 625 pg/ml (normal average 11 +/- 16 pg/ml); the true glucagon accounted for 1435 pg/ml (normal average 31 +/- 29 pg/ml); and the small glucagon immunoreactive fraction (approximately 2000 mol wt) measured 35 pg/ml (normal average 26 +/- 18 pg/ml). The high levels of LGI, considered a candidate for proglucagon, may reflect the increased secretory activity of the tumor.     

The contribution of the zona fasciculata and glomerulosa to plasma 11-deoxycorticosterone levels in man.

Using a newly developed radioassay method, plasma 11-deoxycorticosterone (DOC) levels were studied in 6 human volunteers for diurnal variation and for response to ACTH, metyrapone, dexamethasone, and low or high dietary sodium. DOC reached its peak of 6.4 +/- 1.2 ng/100 ml at 8:00 AM, and its nadir of less than 1 ng/100 ml at midnight. Corresponding plasma cortisol values were 14.1 +/- 1.4 mug/100 ml and 5.9 +/- 1.3 mug/100 ml respectively. After intramuscular ACTH (Cortrosyn 0.25 mg), DOC rose to 28.7 +/- 1.8 ng/100 ml in 1 h. Dexamethasone treatment for 3 days reduced DOC to less than 1 ng/100 ml in all 6 subjects. Oral metyrapone for 24 h resulted in dramatically elevated DOC levels of 1568 +/- 183 ng/100 ml. High dietary sodium did not affect DOC levels which averaged 5.6 +/- 0.7 ng/100 ml. After 3 days of sodium restriction, DOC levels were unchanged at 4.8 +/- 0.5 ng/100 ml (P greater than 0.9) despite high plasma renin activity and elevated plasma and urinary aldosterone. Dexamethasone was then added, and the diet continued for a further 2 days. In contrast to the effect of dexamethasone during ad lib sodium intake, DOC was not suppressed but slightly elevated to 8.6 +/- 1.4 ng/100 ml (P = 0.01), whereas plasma aldosterone decreased from 32.9 +/- 1.5 to 22.1 +/- 2.1 ng/100 ml. Seven additional subjects underwent the same diet for 5 days without the addition of dexamethasone. There was no change in their DOC values. It is concluded that the zona fasciculata is the main source of DOC, but in the presence of dexamethasone a contribution from the zona glomerulosa during sodium depletion is uncovered.     

Ovine corticotropin-releasing hormone stimulation test in normal children

We administered ovine corticotropin-releasing hormone (CRH) as a bolus iv injection (1 microgram/kg) to 21 normal boys and girls, aged 6-15 yr. CRH stimulated release of immunoreactive ACTH and cortisol in all children. The peak plasma ACTH and cortisol levels after CRH were 15.7 +/- 9.4 (SD) pg/ml and 14.3 +/- 3.6 micrograms/dl, respectively, in the girls, and 20.7 +/- 9.7 pg/ml and 16.6 +/- 3.3 micrograms/dl, respectively, in the boys. Plasma ACTH and cortisol responsiveness to CRH did not differ between girls or boys, or between children and adults. Cortisol-binding globulin concentrations in plasma did not change with age. We conclude that CRH provides a safe means of stimulating the pituitary-adrenal axis in children.     

An acute rise in serum phosphorus after single-dose oral metyrapone

Metyrapone, an 11 beta-hydroxylase inhibitor, is widely used as a pharmacologic test for ACTH reserve. During studies on the pharmacodynamics of metyrapone and the response of plasma 11-deoxycortisol and cortisol, we fortuitously noted a consistent change in serum phosphate but no other routine laboratory chemistry determination. For these studies 12 control subjects were given oral methyrapone (30 mg/kg) at midnight. Serum phosphate (P) concentration was measured in fasting subjects at 08:00 on the morning before and after the administration of metyrapone. In 11 of 12 subjects, serum P increased from a mean of 3.6 +/- 0.7 (SD) mg/100 ml to a mean of 4.2 +/- 0.07 (SD) mg/100 ml on the morning following the drug. No increase in P was noted following the same dose of metyrapone in four patients on acute or chronic steroid therapy or in patients with primary or secondary hypoadrenocorticism. In addition, two addisonian patients were given either a saline or a hydrocortisone infusion for four hours. While the hydrocortisone infusion resulted in a drop in serum P, there was no decrease during saline infusions. These findings suggest that an acute rise in serum P after a single dose of metyrapone might be a rapid indicator of adrenocortical blockade leading to increased ACTH secretion, and cortisol and/or ACTH might play a role in P homeostasis.