PATTERNS OF PLASMA CORTISOL AND ACTH CONCENTRATIONS IN PATIENTS WITH ADDISON''S DISEASE TREATED WITH CONVENTIONAL CORTICOSTEROID REPLACEMENT

Plasma cortisol and adrenocorticotrophin hormone (ACTH) profiles were estimated in twelve patients with Addison's disease following randomized oral administration of either cortisone acetate (25 mg) or hydrocortisone (20 mg) alternately, at 0900 h on consecutive days. Normal corticosteroid replacement therapy was discontinued from 1200 h on the day prior to the study period. In four patients elevated basal plasma ACTH concentrations were not suppressed to the limit of detection following the administration of either drug, and in three of these no suppression was found following the prolonged administration of pharmacological doses of dexamethasone. Diminished sensitivity of pituitary ACTH secretion to cortisol inhibition may result from chronic loss of negative feedback before and/or after diagnosis and treatment. In three patients elevated basal plasma ACTH concentrations were suppressed adequately during the administration of either drug, but in five, low basal ACTH concentrations following corticosteroid withdrawal suggested chronic inhibition of anterior pituitary corticotrophs by over-replacement with glucocorticoid. However, further study is necessary to determine whether the estimation of ACTH profiles is a more accurate reflection of the adequacy of corticosteroid replacement than the estimation of cortisol profiles alone, and whether this estimation leads to an improvement in patient management. Hydrocortisone (20 mg) achieved higher mean cortisol levels and lower mean ACTH levels than cortisone acetate (25 mg), but either drug may be suitable for glucocorticoid replacement provided the dose is tailored to the individual needs.     

ON THE SITE OF ACTION OF THE ANTI-ADRENAL STEROIDOGENIC EFFECT OF ETOMIDATE AND MEGESTROL ACETATE

The sites of action of the anti-steroidogenic action of etomidate and megestrol acetate have been established with a novel in vitro approach based upon the inhibition of cortisol (Co) secretion by dispersed guinea-pig adrenal cells. The cells were challenged with the Co precursor steroids (all at 10(-5) mol/l) pregnenolone (Pe), 17-hydroxy-pregnenolone (17-Pe), progesterone (Po), 17-hydroxyprogesterone (17-Po), 21-deoxycortisol (21-DOC) and 11-deoxycortisol (11-DOC), or 1-24 adrenocorticotrophin (ACTH, 100 ng/l) in the presence or absence of either etomidate, megestrol acetate, metyrapone or trilostane (all at 5 X 10(-5) mol/l). In the absence of drug, the steroid precursors or ACTH provoked a cortisol secretion of greater than 14 times that secreted by cells incubated in their absence. ACTH-stimulated Co secretion was inhibited by greater than 85% by all the drugs employed. In the presence of trilostane and megestrol acetate, Co secretion provoked by the delta 4 3-keto steroids (Po, 17-Po, 21-DOC and 11-DOC) was similar to the controls. However, with the delta 5, 3 beta-hydroxy steroids, 17-Pe and Pe, Co secretion was inhibited by greater than 57% in the presence of these drugs. In contrast, etomidate and metyrapone inhibited Co secretion by greater than 60% when 11-deoxycortisol was employed, indicative of a block at 11 beta-hydroxylase, the final step in the cortisol biosynthetic pathway. Similar results were seen with Pe, 17-Pe, Po and 17-Po, all of which are converted to cortisol via a biosynthetic route which includes catalysis by 11 beta-hydroxylase.(ABSTRACT TRUNCATED AT 250 WORDS)     

RADIOIMMUNOASSAY OF PLASMA 18-HYDROXY-ll-DEOXYCORTICOSTERONE AND ITS RESPONSE TO ACTH

A radioimmunoassay for the measurement of 18-OH-DOC in plasma was developed using an antiserum raised against the gamma-lactone derivative. The steroids with the greatest degree of cross reaction were 18-OH-corticosterone-gamma-lactone and aldosterone-gamma-lactone which showed cross-reactivities of 1.96% and 0.47% respectively. These and other interfering steroids were eliminated by chromatography of the extracts on columns of Sephadex LH-20. The lowest limit of detection of 18-OH-DOC in 1 ml of plasma corresponded to 33 pmol-1. The intra-assay precision was 9.7, 4.8 and 2.6% at 102.0, 316.1 and 1144.0 pmol 1(-1) respectively and the interassay precision was 15.3 and 5.4% at 71.3 and 404.7 pmol 1(-1) respectively. The amount of 18-OH-DOC measured (y) which showed a high degree of correlation (r = 0.999) with the amount added (x) to plasma in the range 240--1920 pmol 1(-1) could be predicted from the linear least squares equation y = 1.006x + 31.3. The concentration of 18-OH-DOC in ten normal subjects was 172.1 +/- 39.1 pmol 1(-1) at 09.00 h, 100.9 +/- 16.9 pmol 1(-1) at 12.00 h and 95.8 +/- 33.3 pmol 1(-1) at 16.30 h. Plasma 18-OH-DOC and cortisol levels were measured after various intravenous doses of ACTH in three patient with esential hypertension. Lower doses of ACTH caused similar percentage increases in both hormones but higher doses caused considerably greater increases in 18-OH-DOC. These results confirm the ACTH dependancy of 18-OH-DOC secretion.     

EFFECTS OF HIGH-DOSE AND LOW-DOSE NALOXONE ON PLASMA ACTH IN PATIENTS WITH ACTH HYPERSECRETION

The effect of a high (5.4 mg/h) and a low (0.8 mg/h) dose of naloxone (i.v. over a period of 90 min) on ACTH secretion was compared with placebo in patients with Addison's disease, congenital adrenal hyperplasia, Cushing's disease or Nelson's syndrome. In seven patients with primary adrenal insufficiency the high dose of naloxone provoked a significant increase of plasma ACTH concentrations (P less than 0.02) whereas the low dose of naloxone failed to influence ACTH secretion. In six patients with ACTH dependent Cushing's disease or Nelson's syndrome both doses failed to alter plasma ACTH levels. These results support the concept of inhibitory delta- or kappa-opiate receptors in the regulation of ACTH secretion. In patients with Cushing's disease or Nelson's syndrome ACTH secretion is insensitive to naloxone, presumably because of an autonomous pituitary adenoma or hypothalamic derangement.     

THE EFFECT OF SHORT- AND LONG-TERM CORTICOSTEROID TREATMENT ON SLEEP-ASSOCIATED GROWTH HORMONE SECRETION

Eight healthy medical studients and four renal transplant patients had blood sampled two or three times hourly throughout EEG monitored nocturnal sleep. This was carried out on the healthy subjects for a total of 12 nights without medication (control nights asleep), a total of 12 nights following 40 mg of flucortolone the previous morning, and a total of 6 nights with similar blood sampling when sleep was prevented (control nights awake). Four renal transplant patients who were receiving long-term therapy with prednisolone were similarly studied (total of 7 nights asleep). Circulating corticosteroid and growth hormone (GH) levels were determined. A peak of GH was seen during the first 2 h of sleep on the control nights when slow-wave sleep predominated. The GH peak was absent on the control nights awake. The pattern of plasma corticosteroid levels was identical during control nights asleep and awake. Both single-dose and chronic corticosteroid administration inhibited the GH peak associated with slow-wave sleep. Chronic corticosteroid therapy, but no single-dose administration in the morning, suppressed the circadian rise of plasma corticosteroids which normally occurs late in sleep.     

CIRCANNUAL RHYTHMS OF PLASMA GROWTH HORMONE, THYROTROPIN AND THYROID HORMONES IN PREPUBERTY

To clarify the occurrence of circannual GH, TSH, T4 and T3 rhythms in prepuberty we have been studying, for a four year period, 150 healthy subjects, aged 6-10, by cross-sectional design. Plasma samples were taken at 0800 h and all hormones were measured by RIA. The occurrence of any circannual rhythm was statistically investigated by the cosinor method. A significant rhythm was validated (P = 0.02) only in TSH secretion, with annual crest time in December; GH, T4, T3 did not show a circannual rhythm. Our results seem to strengthen the hypothesis that the thyroid hormones, at least before puberty, do not play an important role in the regulation of circannual TSH periodicity.     

PLASMA AND CYST FLUID LEVELS OF A5 AND A4 STEROID HORMONES IN WOMEN WITH GROSS CYSTIC BREAST DISEASE

delta 5 and delta 4 steroid levels were studied in the plasma and cyst fluid of women with gross cystic breast disease (GCBD). In luteal phase a significant increase in plasma levels (mean +/- SEM) of DHA (11.2 +/- 2.4 ng/ml), DHAS (1.45 +/- 0.6 micrograms/ml) and cortisol 277 +/- 15.7 ng/ml) was found; in follicular phase the mean levels were 4.09 +/- 0.47 ng/ml for DHA, 0.65 +/- 0.08 microgram/ml for DHAS and 190 +/- 46.3 micrograms/ml for cortisol. The DHA/DHAS and cortisol/androstenedione ratios were significantly higher in the plasma and lower in the cyst fluid of GCBD patients, than in the plasma of controls; the androstenedione/DHA ratio was higher in the cyst fluid than in the plasma of controls. The hormonal situation of the GCBD patients thus differed from that of the controls both in the plasma and cyst fluid, particularly as regards the delta 5 steroids.     

PLASMA LEVELS OF NORETHINDRONE AFTER SINGLE ORAL DOSE ADMINISTRATION OF NORETHINDRONE AND LYNESTRENOL

Single oral doses of 0.3 mg, 0.5 mg and 5 mg Norethindrone (NET) and 0.5 mg and 5 mg Lynestrenol (lyn) were given to five women. Lynestrenol is probably metabolized through NET and exerts its main biological activity as NET. Plasma concentrations of NET were determined by a radioimmunoassay at different intervals after administration of the tablets. Peak concentrations of NET were found within two hours after intake of each table. The plasma half life of Net after NET and lyn administration for the period 8-24 h was 8-11 h. No significant difference was found between the half life of NET and the NET tablets and after the lyn tablets. When 5 mg NET was given the plasma half life of NET for the period 24-72 h was around 10 h and this was significantly shorter than the half-life of NET after 5 mg lyn, which was 16 1/2 h. The systemic availability of the drugs was estimated by calculating and comparing the areas under the plasma concentration versus time curve (AUC). 0-24 H. The AUC 0.24 after 0.3 MG NET was almost identical to the AUC 0.24 after 0.5 mg lyn. The AUC 0-24 after 0.5 mg NET was significantly larger than after 0.5 lyn. No difference was found between the AUC 0-24 after 5 mg lyn and 5 mg NET. This study supports the concept of a conversion from lyn to NET. It also shows that there were only minor pharmacokinetic differences between the drugs when all samples were measured as NET.     

NYCTOHEMERAL VARIATION AND SUPPRESSIBILITY OF PLASMA ACTH IN VARIOUS STAGES OF CUSHING''S DISEASE

In order to define nyctohemeral plasma ACTH secretory patterns, frequency plasma ACTH samples were obtained in seven patients with untreated Cushing's disease (i.e. pituitary-dependent Cushing's syndrome), five Cushing's patients treated by bilateral adrenalectomy, four of whom had Nelson's syndrome, and one patient with 21-hydroxylase deficiency (congenital adrenal hyperplasia). A nyctohemeral rhythm of plasma ACTH concentration was apparent in the one patient with the adrenogenital syndrome but not in those with Nelson's syndrome or Cushing's disease. The effect of graded doses of dexamethasone, 2,8 or 32 mg per 24 h period, on plasma ACTH concentrations was studied in patients with untreated or treated Cushing's disease or Nelson's syndrome. In all of these hypercorticotrophic states, the mean plasma ACTH concentraton was not significantly affected by the smallest dose of dexamethasone, was partially suppressed by the intermediate dose, and further suppressed by the largest dose. In contrst, the patient with congenital adrenal hyperplasia and elevated plasma ACTH concentrations showed complete suppression of plasma ACTH levels following the smallest dose of dexamethasone. These findings indicate that there is resistance to ACTH suppression by dexamethasone in all stages of Cushing's disease and suggest that negative feedback of glucocorticoids may be involved in the pathogenesis of this disease.     

THE EFFECT OF CYPROHEPTADINE AND/OR BROMOCRIPTINE ON PLASMA ACTH LEVELS IN PATIENTS CURED OF CUSHING''S DISEASE BY BILATERAL ADRENALECTOMY

Cyproheptadine and bromocriptine have been reported to be therapeutic in suppressing ACTH levels in Cushing's disease and Nelson's syndrome. However, there have been only scattered reports of their effect in suppressing raised ACTH levels found in patients cured of Cushing's disease by bilateral adrenalectomy. In order to assess whether these agents could prove beneficial in such patients we studied 12 patients previously treated with bilateral adrenalectomy alone for Cushing's disease before and after 3 weeks of cyproheptadine and/or bromocroptine therapy. All had raised plasma ACTH values but no patient had evidence of a pituitary macroadenoma. Plasma ACTH and cortisol were sampled 2-hourly for 24 h. Neither drug regime led to any change in plasma levels of cortisol for 24 h after a 20 mg dose of oral hydrocortisone. Plasma ACTH (mean +/- SEM) showed a small but significant overall reduction (523 +/- 45 vs 392 +/- 34 ng/l; P less than 0.05) while on bromocriptine alone (5 mg given at 0800 and 1800 h, n = 5). When each time point was analysed individually this reduction was significant at only five out of 13 time points. At 0400 h plasma ACTH (mean +/- SEM) was 758.4 +/- 298.1 vs 380.2 +/- 166.6; 0600 h, 795 +/- 288.7 vs 477.8 +/- 191.7; 1200 h, 266.8 +/- 106.2 vs 187.0 +/- 80.3; 1400 h, 470.0 +/- 239.0 vs 302.0 +/- 135.9; 1600 h, 548.6 +/- 262.5 vs 394.2 +/- 178.5 ng/l (P less than 0.05). There was no significant change in plasma ACTH during treatment with the combination of bromocriptine and cyproheptadine.(ABSTRACT TRUNCATED AT 250 WORDS)     

EFFECTS OF INHIBITION OF CHOLESTEROL SYNTHESIS BY SIMVASTATIN ON THE PRODUCTION OF ADRENOCORTICAL STEROID HORMONES AND ACTH

Simvastatin, a derivative of lovastatin, is a potent inhibitor of cholesterol biosynthesis and may interfere with steroid hormone production, for which cholesterol is required. In a single-blind, placebo-controlled study, 24 patients with severe primary hypercholesterolaemia (mean serum cholesterol +/- SD = 10.74 +/- 1.59 mmol/l) were treated with simvastatin 40 mg per day for 8 weeks. Before and after treatment, the following parameters were evaluated: basal levels of ACTH, cortisol, androstenedione, dehydroepiandrosterone and 17-hydroxyprogesterone; urinary excretion of free cortisol; the cortisol response after short-term infusion of ACTH; the ACTH and cortisol response during insulin-induced hypoglycaemia. Total serum cholesterol decreased by 35.0 +/- 8.1% (P less than 0.001) and low-density lipoprotein (LDL) cholesterol by 39.8 +/- 9.8% (P less than 0.001); high-density lipoprotein (HDL) increased by 9.2 +/- 11.1% (P less than 0.001). Basal levels of ACTH were higher after simvastatin (2.9 +/- 1.9 pmol/l vs 4.1 +/- 2.9 pmol/l; P less than 0.05) whereas basal levels of steroid hormones were not significantly changed. The excretion of free cortisol was unaltered. The peak cortisol after ACTH infusion was lower after treatment (0.87 +/- 0.23 mumol/l vs 0.78 +/- 0.10 mumol/l; P less than 0.05), but was unaltered during insulin-induced hypoglycaemia. We conclude that simvastatin lowers serum cholesterol without clinically relevant effects on the adrenocortical steroid hormone secretion and the hypothalamic-pituitary-adrenal axis.     

THE EFFECT OF PROPRANOLOL ON THYROID HORMONES AND OXYGEN CONSUMPTION IN THYROTOXICOSIS

The possibility that propranolol may exert its beneficial actions in thyrotoxicosis by an effect on thyroid hormone concentrations has been investigated by measuring these and oxygen consumption in a group of thyrotoxic patients before and after treatment with propranolol. Following treatment a significant fall in plasma T3 concentration and oxygen consumption occurred and a direct correlation was found between these two variables. Propranolol may, therefore, exert some of its beneficial effects in thyrotoxicosis by an action on T3 metabolism.     

EFFECT OF WEIGHT-LOSS ON PLASMA AND URINARY LEVELS OF URIC ACID

Fifteen overweight subjects, ten men and five women, six of them with gout, reduced their weight on a low-calorie diet. Plasma and urinary levels of uric acid were estimated while the subjects were taking a low-purine diet before and after the period of weight-loss, which ranged from 4 to 22 kg. After weight-loss, plasma-uric-acid fell in twelve of the fifteen subjects by a mean decrease of 0·8 mg. per 100 ml. Changes in urinary urate were not consistent. This influence of body-weight upon the plasma level of uric acid may be responsible for the association between these two variables which has been observed in epidemiological and clinical studies.     

EFFECT OF MECLASTINE, A SELECTIVE H1 RECEPTOR ANTAGONIST, UPON ACTH RELEASE

To elucidate further the role of histamine in the control of ACTH secretion we investigated the effect of the selective H1 receptor antagonist meclastine on the ACTH response to insulin hypoglycaemia and to metyrapone-induced hypocortisolaemia in normal subjects. Intravenous meclastine (4.8 mg/90 min) significantly inhibited the hypoglycaemia-induced ACTH and cortisol increase whereas serum GH and PRL concentrations were unaffected. Orally administered meclastine (3 X 2 mg) also reduced the ACTH feedback response to cortisol deficiency in a modified metyrapone test, compared to a placebo. Our findings support the concept of an excitatory influence of histamine upon ACTH secretion via H1 receptors, possibly by stimulation of CRF release.