Seated saline infusion test in predicting subtype diagnosis of primary aldosteronism.

CONTEXT: Although saline infusion test is widely used as a confirmatory test for primary aldosteronism (PA), it is reportedly less sensitive in patients in whom aldosterone is responsive to the upright position by performing it in recumbent position. Based on a single-centre experience, seated saline infusion test (SSIT) has been reported to be highly sensitive and superior to recumbent testing in identifying both unilateral and bilateral forms of PA. However, due to limited participants number, the utility of SSIT needs to be validated in other series. OBJECTIVE: This study aimed to evaluate the accuracy of SSIT in determining the PA subtypes compared with adrenocorticotropic hormone stimulation test under dexamethasone suppression (Dex-AT). PATIENTS AND SETTING: Sixty-four patients with PA who underwent both SSIT and Dex-AT were included. Subtype diagnosis of PA was determined by adrenal venous sampling (AVS) (16 unilateral and 48 bilateral forms). MAIN OUTCOME MEASURE: Plasma aldosterone concentrations (PACs) were measured after SSIT and Dex-AT. RESULTS: The area under the receiver operating characteristic (ROC) curve for diagnosing unilateral PA was greater in SSIT than that in Dex-AT (0.907 vs. 0.755; P = .023). ROC curve analysis predicted optimal cut-off PACs of 13.1 ng/dL (sensitivity, 93.8%; specificity, 79.2%) for SSIT and 34.2 ng/dL (sensitivity, 75.0%; specificity, 68.8%) for Dex-AT. CONCLUSIONS: Seated saline infusion test has superior accuracy in subtype diagnosis of PA compared with Dex-AT. SSIT can be a sensitive test for determining patients who require AVS prior to surgery.

Adsorption effects of the doping relevant peptides Insulin Lispro, Synachten, TB-500 and GHRP 5.

The tendency of peptides to adsorb to surfaces can raise a concern in variety of analytical fields where the qualitative/quantitative measurement of low concentration analytes (ng/mL-pg/mL) is required. To demonstrate the importance of using the optimal glassware/plasticware, four doping relevant model peptides (GHRP 5, TB-500, Insulin Lispro, Synachten) were chosen and their recovery from various surfaces were evaluated. Our experiments showed that choosing expensive consumables with low-bind characteristics is not beneficial in all cases. A careful selection of the consumables based on the evaluation of the physico/chemical features of the peptide is recommended.

Adrenal Suppression With Chronic Topical Corticosteroid Use in Psoriasis Patients.

BACKGROUND: Topical corticosteroids (TCS) are typically used for extended periods of time for chronic skin conditions, including psoriasis. Chronic TCS use may result in side effects similar to those of systemic corticosteroids. Patients may have subclinical adrenal suppression and be unaware of their risk in the case of serious trauma.
OBJECTIVE: The objective of this study was to investigate the real world effects of chronic TCS use and its effects on adrenal suppression in a chronic disease such as psoriasis.
MATERIALS: This retrospective study utilized data from screening visits of a psoriasis clinical trial in which subjects had been on chronic TCS.
RESULTS: In this study, subjects with moderate to severe psoriasis affecting 16-20% of total body surface area (BSA) and using high-potency TCS at screening had a lower post-cosyntropin cortisol level (18.83 mcg/dL) compared to those with moderate psoriasis involving 10-15% of total BSA and using lower potency TCS at screening (23.22 mcg/dL; P=0.03). Both subject groups had lower post-cosyntropin cortisol levels compared to normal, healthy adults (P<0.001 for both).
CONCLUSION: This suggests that real world chronic use of high potency TCS over a larger BSA may result in silent adrenal suppression.

J Drugs Dermatol. 2016;15(8):945-948.

Primary vs secondary adrenal insufficiency: ACTH-stimulated aldosterone diagnostic cut-off values by tandem mass spectrometry.

OBJECTIVES: To validate the diagnostic utility of Cortrosyn(™) stimulated aldosterone in the differentiation of primary (PAI) and secondary adrenal insufficiency (SAI) and to evaluate the effect of urine sodium levels and posture on test performance. DESIGN: Cross-sectional study. METHODS: Healthy volunteers (HV; n = 46) and patients with PAI (n = 26) and SAI (n = 29) participated in the study. Testing included cortisol and aldosterone (by liquid-chromatography tandem mass spectrometry) measurements at baseline and 30 and 60 min after 250 µg Cortrosyn(™). Plasma corticotropin (ACTH), renin activity (PRA) and urine spot sodium as a proxy for 24-h urine sodium excretion were measured at baseline. The effect of a sitting or semifowlers posture was evaluated in healthy volunteers. RESULTS: A Cortrosyn(™)-stimulated aldosterone level of 5 ng/dl (0·14 nmol/l) had 88% sensitivity and positive predictive value and 89·7% specificity and negative predictive value for distinguishing PAI from SAI. Spot urine sodium levels showed a strong correlation with peak aldosterone levels (r = -0·55, P = 0·02, n = 18) in the SAI but not PAI or HV groups. Posture did not have a significant effect on results. CONCLUSIONS: Once diagnosed with adrenal insufficiency, a stimulated aldosterone value of 5 ng/dl (0·14 nmol/l) works well to differentiate PAI from SAI. However, clinicians should be aware of the possible effect of total body sodium as reflected by spot urine sodium levels on aldosterone results. A 24-h urine sodium measurement may be helpful in interpretation.

Determination of Synacthen(®) in dried blood spots for doping control analysis using liquid chromatography tandem mass spectrometry.

Dried blood spot (DBS) sampling, a technique used for taking whole blood samples dried on a filter paper, was initially reported in 1963 by Robert Guthrie. While the diagnostic analysis of metabolic disorders in newborns was the focus of investigations at that time, the number of established applications for preclinical drug development, toxicological studies, and therapeutic drug monitoring increased enormously in the last decades. As a consequence of speed, simplicity, and minimal invasiveness, DBS recommends itself as the preferential technique in sports drug testing. The present approach highlights for the first time the development of a screening assay for the analysis of the synthetic human adrenocorticotropic hormone tetracosactide hexaacetate (Synacthen(®)) in DBS using liquid chromatography tandem mass spectrometry. Highly purified sample extracts were obtained by an advanced sample preparation procedure including the addition of an internal standard (d8-tetracosactide) and immunoaffinity purification. The method's overall recovery was 27.6 %, and the assay's imprecision was calculated between 8.1 and 17.9 % for intraday and 12.9 to 20.5 % for interday measurements. Stability of the synthetic peptide in DBS was shown for at least 10 days at room temperature and presents a major benefit, since a rapid degradation in conventionally applied matrices such as urine or plasma is well known. With a limit of detection of 50 pg/mL, a detection window of several hours is expected considering reported steady-state plasma levels of 300 pg/mL after intramuscular application of Synacthen(®) Depot (1 mg). The analysis of authentic DBS samples within the scope of an administration study with 250 µg Synacthen(®) (short stimulation test) demonstrated the great potential of the developed assay to simplify the analysis of Synacthen(®) for doping control purposes.

Simultaneous quantification and qualification of synacthen in plasma.

Tetracosactide (Synacthen), a synthetic analogue of adrenocorticotropic hormone (ACTH), can be used as a doping agent to increase the secretion of glucocorticoids by adrenal glands. The only published method for anti-doping control of this drug in plasma relies on purification by immunoaffinity chromatography and LC/MS/MS analysis. Its limit of detection is 300 pg/mL, which corresponds to the peak value observed 12 h after 1 mg Synacthen IM administration. We report here a more sensitive method based on preparation of plasma by cation exchange chromatography and solid-phase extraction and analysis by LC/MS/MS with positive-mode electrospray ionization using 7-38 ACTH as internal standard. Identification of Synacthen was performed using two product ions, m/z 671.5 and m/z 223.0, from the parent [M + 5H](5+) ion, m/z 587.4. The recovery was estimated at 70%. A linear calibration curve was obtained from 25 to 600 pg/mL (R² > 0.99). The lower limit of detection was 8 pg/mL (S/N > 3). The lower limit of quantification was 15 pg/mL (S/N > 10; CV% < 20%). The performance of the method was illustrated by an 8-h kinetic analysis of plasma samples from nine subjects submitted to IM injections of either Synacthen® (five subjects) or Synacthen® Depot, the slow-release form of the drug (four subjects). Concentrations of Synacthen between 16 and 310 pg/mL were observed. A sensitive method for quantitation of Synacthen in plasma is proposed for anti-doping control analyses.

Residual Corticosteroid Production in Autoimmune Addison Disease.

CONTEXT: Contrary to current dogma, growing evidence suggests that some patients with autoimmune Addison disease (AAD) produce corticosteroids even years after diagnosis. OBJECTIVE: To determine frequencies and clinical features of residual corticosteroid production in patients with AAD. DESIGN: Two-staged, cross-sectional clinical study in 17 centers (Norway, Sweden, and Germany). Residual glucocorticoid (GC) production was defined as quantifiable serum cortisol and 11-deoxycortisol and residual mineralocorticoid (MC) production as quantifiable serum aldosterone and corticosterone after > 18 hours of medication fasting. Corticosteroids were analyzed by liquid chromatography-tandem mass spectrometry. Clinical variables included frequency of adrenal crises and quality of life. Peak cortisol response was evaluated by a standard 250 µg cosyntropin test. RESULTS: Fifty-eight (30.2%) of 192 patients had residual GC production, more common in men (n = 33; P < 0.002) and in shorter disease duration (median 6 [0-44] vs 13 [0-53] years; P < 0.001). Residual MC production was found in 26 (13.5%) patients and associated with shorter disease duration (median 5.5 [0.5-26.0] vs 13 [0-53] years; P < 0.004), lower fludrocortisone replacement dosage (median 0.075 [0.050-0.120] vs 0.100 [0.028-0.300] mg; P < 0.005), and higher plasma renin concentration (median 179 [22-915] vs 47.5 [0.6-658.0] mU/L; P < 0.001). There was no significant association between residual production and frequency of adrenal crises or quality of life. None had a normal cosyntropin response, but peak cortisol strongly correlated with unstimulated cortisol (r = 0.989; P < 0.001) and plasma adrenocorticotropic hormone (ACTH; r = -0.487; P < 0.001). CONCLUSION: In established AAD, one-third of the patients still produce GCs even decades after diagnosis. Residual production is more common in men and in patients with shorter disease duration but is not associated with adrenal crises or quality of life.

Intramuscular administration of a low dose of ACTH for ACTH stimulation testing in dogs.

OBJECTIVE: To compare adrenal gland stimulation achieved following administration of cosyntropin (5 microg/kg [2.3 microg/lb]) IM versus IV in healthy dogs and dogs with hyperadrenocorticism. DESIGN: Clinical trial. Animals-9 healthy dogs and 9 dogs with hyperadrenocorticism. PROCEDURES: In both groups, ACTH stimulation was performed twice. Healthy dogs were randomly assigned to receive cosyntropin IM or IV first, but all dogs with hyperadrenocorticism received cosyntropin IV first. In healthy dogs, serum cortisol concentration was measured before (baseline) and 30, 60, 90, and 120 minutes after cosyntropin administration. In dogs with hyperadrenocorticism, serum cortisol concentration was measured before and 60 minutes after cosyntropin administration. RESULTS: In the healthy dogs, serum cortisol concentration increased significantly after administration of cosyntropin, regardless of route of administration, and serum cortisol concentrations after IM administration were not significantly different from concentrations after IV administration. For both routes of administration, serum cortisol concentration peaked 60 or 90 minutes after cosyntropin administration. In dogs with hyperadrenocorticism, serum cortisol concentration was significantly increased 60 minutes after cosyntropin administration, compared with baseline concentration, and concentrations after IM administration were not significantly different from concentrations after IV administration. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that in healthy dogs and dogs with hyperadrenocorticism, administration of cosyntropin at a dose of 5 microg/kg, IV or IM, resulted in equivalent adrenal gland stimulation.

ACTH 1-24 inhibits proliferation of adrenocortical tumors in vivo.

OBJECTIVES: Although several lines of evidence suggest that the overall effects of the ACTH receptor, melanocortin 2 receptor (MC2-R), mediated signal transduction on adrenocortical growth and tumorigenesis are anti-proliferative, activation of MC2-R induces mitogens like jun, fos, and myc and activates the MAPK pathway. In vivo, potential effects of endogenous ACTH on adrenal tumori-genesis can not be separated from effects of other POMC derived peptides. METHODS: Murine adrenocortical tumor cells that lack MC2-R expression (Y6(pcDNA)) and Y6 cells stablely transfected with MC2-R (Y6(MC2-R)) were generated. Presence of functional MC2-R was demonstrated by RT-PCR and Western blot using an antibody for phosphorylated CREB. As a syngenic tumor model, LaHeF1/J mice simultaneously received 10(7) Y6(MC2-R) and Y6(pcDNA) subcutaneously, giving rise to MC2-R positive and negative tumors within the same animal. Animals were treated for 3 weeks in groups of 12 according to the following schedule: group A, control animals receiving saline injection; group B, animals receiving 5.7 ng/injection of a slow release formula of ACTH 1-24 administered i.p. three times a week (aiming at a low physiologic dose); and group C, animals receiving 57 ng/injection of ACTH 1-24 (high physiological dose). RESULTS: Twenty days of ACTH 1-24 treatment did not significantly affect corticosterone levels, endogenous ACTH levels or adrenal and thymus weight compared with saline injection. However, ACTH 1-24 treatment of group B and C mice significantly reduced tumor weight in MC2-R positive tumors in a dose dependent manner (P = 0.03), while no significant difference in tumor mass was observed in MC2-R negative tumors. PCNA and TUNEL staining, together with morphological characterization, demonstrated that these in vivo effects were due to reduced proliferation, while apoptosis and cellular hypertrophy within the tumor remained unchanged. CONCLUSION: MC2-R expression is associated with a less aggressive adrenal tumor phenotype and anti-proliferative effects can be amplified through stimulation with physiological doses of ACTH.

Detection of tetracosactide in plasma by enzyme-linked immunosorbent assay (ELISA).

As a synthetic analogue of adrenocorticotropic hormone (ACTH), tetracosactide is prohibited in sport by the World Anti-Doping Agency (WADA). An enzyme-linked immunosorbent assay (ELISA) method is proposed for detection of this drug in plasma. Since its structure corresponds to the 24 N-terminal of the 39 amino acids of the natural endogenous peptide ACTH, tetracosactide can be detected with a commercial ELISA kit for ACTH that uses antibodies, the epitopes of which are located in the 1-24 part of ACTH. However, an essential condition for detection specificity is the preliminary total clearance of endogenous ACTH in the plasma samples. This is achieved by a preparative step based on cation-exchange chromatography before ELISA. The method is specific and sensitive (LOD: 30 pg/mL) and may be used as a screening analysis in anti-doping control. The pre-analytical conditions are shown to be of the upmost importance and recommendations for blood collection (EDTA tubes), sample transport (4 °C) and plasma sample storage (-20 °C) are presented.

Hypothalamus-pituitary dysfunction is common in patients with stable cirrhosis and abnormal low dose synacthen test.

BACKGROUND: Adrenal insufficiency is often present in cirrhosis. We hypothesize that a prolonged adrenocorticotropic hormone (ACTH) stimulus can restore cellular capacity of adrenal glands to secrete cortisol. Aim of our study was to assess adrenal responsiveness to prolonged ACTH stimulation in cirrhotics. METHODS: Prospective observational study in 121 consecutively admitted cirrhotic patients undergoing a low dose short synacthen test and plasma ACTH measurement using a chemiluminescence immunoassay. Long synacthen test was performed if the low dose was abnormal. RESULTS: 46 patients had abnormal low dose short test (38%), and 29 underwent the long test: 41% showed normal response (Group 1), 55% showed delayed response (Group 2) and 1 had abnormal response (4%). Baseline ACTH levels did not significantly differ between the two groups. Median basal cortisol was higher in Group 1 (296 vs. 198 nmol/L; p=0.02). Using ROC curve basal cortisol <254 nmol/L was associated with a delayed long synacthen test response (AUC 0.78, p=0.001) with good accuracy (sensitivity 67%, specificity 81%). CONCLUSION: A delayed cortisol response after a prolonged ACTH stimulation is found in over fifty percent of cirrhotics with abnormal low dose short synacthen test, confirming that the mechanism of hypoadrenalism in these patients could be related both to adrenal cellular dysfunction and hypothalamus-pituitary adrenal axis impairment.

Salivary cortisol and cortisone responses to tetracosactrin (synacthen).

BACKGROUND: To establish cutoff values for salivary liquid chromatography tandem mass spectroscopy cortisol and cortisone in defining adequate adrenocortical function during a standard synacthen test. METHODS: We compared salivary liquid chromatography tandem mass spectroscopy cortisol and cortisone responses to those of serum cortisol measured on the Roche E170 immunoassay analyser and the Abbott Architect i2000 before and 30 min and 60 min following 0.25 mg of intravenous synacthen. RESULTS: Correlations of salivary cortisol and cortisone were bimodal and linear, respectively. Based on these correlations, adequate salivary cortisol and cortisone responses to synacthen were extrapolated from a serum cortisol (Roche) cut-off of 550 nmol/L and defined as 15 nmol/L and 45 nmol/L, respectively. The Abbott method correlated well with the Roche but gave results that were about 20% lower than the Roche method. CONCLUSIONS: Measurement of salivary cortisol and cortisone responses offers an alternative to those of serum cortisol during a synacthen test in the investigation of adrenal hypofunction.

Steroid Profiling by LC-MS/MS in Nonsecreting and Subclinical Cortisol-Secreting Adrenocortical Adenomas.

CONTEXT: Long-term follow-up studies revealed that patients with subclinical hypercortisolism (SH) due to adrenocortical adenomas have an increased incidence of cardiovascular diseases and mortality. No studies have yet investigated the steroid profile and its implications in patients with SH. OBJECTIVE: The objective of the study was to analyze the steroid profile by liquid chromatography-tandem mass spectrometry in sera from patients with unilateral adrenocortical adenomas. DESIGN: This was a cross-sectional study. SETTING: The study was conducted at an outpatient clinic. PARTICIPANTS: Patients with adrenocortical adenomas (nonsecreting, n = 66; SH, n = 28) and 188 age- and sex-matched controls drawn from the general population participated in the study. MAIN OUTCOME MEASURES: Cortisol, 21-deoxycortisol, 11-deoxycortisol, 17-hydroxyprogesterone, androstenedione, dehydroepiandrosterone, T, progesterone, 11-deoxycorticosterone, and corticosterone in the basal condition and after a 1-24 ACTH test, and clinical data were measured. RESULTS: Patients with SH showed lower basal and 1-24 ACTH-stimulated levels of dehydroepiandrosterone and androstenedione than those with nonsecreting adenomas and controls. T was also lower in SH females. Receiver-operating characteristic curves showed that androgens had good accuracy in predicting SH (sensitivity and specificity were 71% and 76% for dehydroepiandrosterone and 69% and 61% for androstenedione, respectively). Increased cortisol and reduced dehydroepiandrosterone levels were independently associated with increased waist circumference. Cortisol was also independently associated with increased number of cardiovascular risk factors in SH patients. After 1-24 ACTH stimulation, the SH patients also showed increased production of 21-deoxycortisol and 11-deoxycorticosterone. CONCLUSIONS: Liquid chromatography-tandem mass spectrometry steroid profile performed for the first time in sera from patients with adrenocortical adenomas showed impaired secretion of several steroids in SH patients. This fingerprint can help in better characterizing the functional status of these tumors.

An LC-MS/MS method for steroid profiling during adrenal venous sampling for investigation of primary aldosteronism.

BACKGROUND: Steroid profiling for diagnosis of endocrine disorders featuring disordered production of steroid hormones is now possible from advances in liquid chromatography with tandem mass spectrometry (LC-MS/MS). Adrenal venous (AV) measurements of aldosterone and cortisol are a standard practice in the clinical work-up of primary aldosteronism, but do not yet take advantage of steroid profiling. METHODS: A novel LC-MS/MS based method was developed for simultaneous measurement of 15 adrenal steroids: aldosterone, corticosterone, 11-deoxycorticosterone, progesterone, pregnenolone, cortisone, cortisol, 11-deoxycortisol, 17-hydroxyprogesterone, androstenedione, dehydroepiandrosterone, dehydroepiandrosterone-sulfate, 21-deoxycortisol, 18-oxocortisol and 18-hydroxycortisol. These were compared in peripheral venous (pV) and AV plasma from 70 patients undergoing AV sampling with and without cosyntropin stimulation. Aldosterone and cortisol levels measured by LC-MS/MS were compared with those measured by immunoassay. RESULTS: Reproducibility of measurements with coefficients of variation ≤10% as well as analytical sensitivity sufficient to measure low pV levels particularly of aldosterone demonstrate the utility of the assay for profiling adrenal steroids in primary aldosteronism. Method comparisons indicated assay and concentration dependent differences of cortisol and aldosterone concentrations measured by immunoassay and LC-MS/MS. Median AV/pV ratios of 11-deoxycortisol (53.0), 17-hydroxyprogesterone (33.4), pregnenolone (62.4), androstenedione (40.6) and dehydroepiandrosterone (33.3) were 2.9- to, 5.4-fold larger than those for cortisol (11.6), with additionally generally larger increases than for cortisol with than without cosyntropin stimulation. CONCLUSION: Our LC-MS/MS assay, in addition to improvements over existing immunoassay measurements of aldosterone and cortisol, offers profiling of 13 other adrenal steroids, providing a potentially useful method for the clinical work-up of patients with primary aldosteronism. In particular, the larger AV/pV ratios of several steroids compared to cortisol suggest more sensitive alternatives to the latter for assessing positioning of AV sampling catheters.

Effect of bilateral splanchnic nerve section on adrenal function in the ovine fetus.

The effect of bilateral splanchnic nerve (SPLX) section in fetal sheep [116-121 days gestational age (dGA)] on subsequent adrenocortical function was investigated. Fetal cortisol release was stimulated by 1) ACTH-(1-24) administration (100 ng/min for 15 min) at 126-129 and at 132-135 dGA, and 2) nitroprusside-induced hypotension (50% reduction in fetal arterial blood pressure for 10 min) at 129-132 and 136-139 dGA. No differences were observed between SPLX and control fetuses (CONT) in basal arterial plasma concentrations of cortisol from 126-141 dGA. A significant effect of fetal age on basal cortisol was observed in both SPLX and CONT fetuses from 126-141 dGA. A significant (P less than or equal to 0.05) increase in fetal arterial concentrations of cortisol was achieved by ACTH-(1-24) infusion in SPLX and CONT and did not differ between groups at either 126-129 or 132-135 dGA. Hypotension induced a significant increase in fetal plasma cortisol concentrations in SPLX and CONT fetuses (P less than or equal to 0.05). SPLX fetuses secreted significantly less cortisol in response to hypotension than CONT fetuses at both 129-132 and 136-139 dGA (P less than 0.05). Fetal arterial plasma concentrations of immunoreactive ACTH in response to hypotension were not different between CONT and SPLX fetuses. We estimated the half-life of endogenous fetal plasma cortisol after both hypotension and infusion of ACTH-(1-24). There were no differences between either method of inducing cortisol release on the endogenous cortisol half-life, nor were any differences in cortisol half-life observed between SPLX and CONT. At 136-139 dGA the adrenomedullary response to hypotension was abolished in SPLX, confirming completeness of denervation. In conclusion, the splanchnic nerves do not appear to be involved in the normal increase in basal fetal plasma cortisol observed in late gestation in fetal sheep. However, splanchnic nerve modulation of secretion of cortisol in response to stress may be involved in the increased fetal adrenal sensitivity to stress observed late in gestation.

A short negative feedback mechanism regulating corticotropin-releasing hormone release.

The effect of ACTH administration on plasma CRH levels was studied. In five patients with Addison's disease and three patients with hypopituitarism, bolus iv injection of 0.25 and 0.5 mg ACTH-(1-24) reduced plasma CRH levels (that had become elevated 48 h after discontinuation of corticosteroid replacement) to near-normal levels at 30-60 min in a dose-dependent manner. Plasma immunoreactive beta-endorphin levels were similarly decreased in patients with Addison's disease. ACTH-(1-24) (0.25 and 0.5 mg) injection failed to inhibit plasma CRH levels in five normal subjects. Basal CRH release from the rat hypothalamic median eminence in vitro was inhibited by 0.22 and 2.2 nM ACTH-(1-24) and ACTH-(1-39) in a dose-dependent manner. These results suggest that in the absence of negative feedback control of ACTH secretion by glucocorticoids, ACTH can regulate its secretion by inhibition of hypothalamic CRH release.

Adrenal gland volume in major depression: relationship to basal and stimulated pituitary-adrenal cortical axis function.

We measured adrenal gland volume and both baseline and stimulated pituitary and adrenal cortical hormones in 35 unmedicated, major depressives and 35 individually matched normal control subjects. Mean adrenal volume in the depressives was significantly larger, by about 38%, than the adrenal volume of their matched controls. Basal plasma adrenocorticotropic hormone (ACTH)1-39 was significantly lower, and basal plasma cortisol was significantly higher, in the patients. In contrast, basal plasma ACTH determined by radioimmunoassay (RIA) was not significantly different between the two groups. The ACTH response to ovine corticotropin-releasing hormone (oCRH), whether measured specifically as ACTH1-39 or by the less-specific RIA, was highly significantly lower in the depressives than in the controls. However, neither the cortisol response to oCRH nor its response to low-dose ACTH 1-24 differed significantly between groups. In both groups of subjects, correlations between adrenal gland volume and all the hormone measures were low, and none represented more than 4% shared variance. In the patients, adrenal volume did not correlate significantly with duration of the present episode, lifetime number of episodes, melancholic subtype, Hamilton Depression Scale total score, or the Hamilton suicidality item. However, adrenal volume was significantly positively related to the somatization factor of the Hamilton scale, which was almost totally accounted for by the specific items of somatic symptoms and somatic anxiety.

Levels of corticotrophin analogues in the blood after infusion into rats.

An isolated rat adrenal cell bioassay was used to measure blood concentrations in rats after infusion of synthetic human ACTH, corticotrophin-(1-24)-tetracosapeptide or [D-Ser1, Lys17, Lys18]corticotrophin-(1-18)-octadecapeptide amide. Lower blood levels were found with the 1-24 peptide than with human ACTH and the highest levels were found with the 1-18 peptide. These results suggest that the 1-24 peptide which is almost equipotent with natural ACTH in vivo may be more potent at the receptor and corroborate findings to this effect obtained with isolated adrenal cells. The high potency and prolonged action of the 1-18 analogue in vivo are also explained by these results. Low arterial blood concentrations of the 1-24 peptide and human ACTH were found during infusion, suggesting that substantial inactivation must be occurring in a single passage through the lungs. The effects of renal ligature on blood concentrations indicated that the kidney is involved in handling the 1-18 peptide and that human ACTH is also cleared by this organ. After infusion the fall in blood concentrations was biphasic. It is suggested that the rapid phase is due to clearance of peptides in the circulation which results in a fall to lower blood concentrations which are sustained by slow release of peptide from binding sites which act as a depot.

Mechanisms of catabolism of corticotrophin-(1--24)-tetracosapeptide in the rat in vivo.

The fragmentation of corticotrophin-(1--24)-tetracosapeptide in vivo has been studied, using tritium-labelled hormone and chromatography, in the rat. After intravenous injection the levels of peptide in the circulation declined rapidly caused by its distribution to the tissues and from 2 min after injection a range of different cleavage products appeared. Many of the fragments in the circulation after 2 min have been identified and in this way cleavage has been shown to occur after residues 1, 2, 8, 15, 16, 17, 19, 20 and 21. It is believed that this is the result of aminopeptidase attack at the NH2 terminal, and of attack on the basic region of the molecule by trypsin-like endopeptidase followed by carboxypeptidase. The sulphoxide has been identified as a major metabolite in some experiments but the extent of its formation was very variable. Seventy per cent of the dose was distributed to the tissue beds by 1 min. Part of this was present, mainly as intact peptide, in liver and kidney but the greater proportion was found in muscle, skin and intestine where extensive degradation had already occurred. Further characterization of the fragments formed in the muscle provided good evidence that this tissue may have been the site of generation of many of the fragments which later appeared in the circulation.

On the meaning of low-dose ACTH(1-24) tests to assess functionality of the hypothalamic-pituitary-adrenal axis.

To analyse further the ACTH(1-24) low-dose test, which is of clinical interest, we have examined the dose-response relationship between plasma ACTH(1-24) and cortisol concentrations after i.v. administration of increasing doses (1, 5 or 250 microg) of ACTH(1-24) as a bolus. In addition, we have measured plasma ACTH(1-39) and cortisol levels after an insulin tolerance test (ITT). Although there was a dose response relationship between plasma ACTH(1-24) immunoreactivity and the dose injected, cortisol peaks were comparable, but lower than those reached after an ITT. Under these experimental conditions, an increase in plasma ACTH as low as 13 pmol/l (i.e. the increase obtained with the 1 microg dose) induced a near maximal cortisol response. Following injection of 1 microg ACTH(1-24), peak ACTH values were short lasting, similar to physiological daily bursts. After injection of 5 microg ACTH(1-24), plasma ACTH concentrations were higher than those reached during an ITT, but clearly shorter lasting. Injection of 250 microg ACTH(1-24) induced strikingly supraphysiological levels of plasma ACTH. We conclude that neither regular nor low-dose ACTH tests can fully reproduce the ITT. Our observations strongly suggest that the low-dose ACTH(1-24) test (1 microg) can be useful to estimate the adrenal sensitivity under basal, physiological conditions.