Hypothalamic-pituitary-adrenal axis activity and vascular function in healthy adults.

OBJECTIVE: The objective of this study is to assess the relationship between hypothalamic-pituitary-adrenal (HPA) axis activity, vascular function and insulin sensitivity in healthy adults. DESIGN: Open observational study. PATIENTS: Thirty healthy adults were studied at the Endocrine Research Unit, Repatriation General Hospital, Adelaide, SA, Australia. MEASUREMENTS: HPA activity was assessed from the serum cortisol 30 min after 1 µg ACTH1-24 (Novartis Pharmaceuticals). Subjects with a cortisol below (n = 15) and above (n = 15) the median were categorized as low and high responders, respectively. Reactive hyperaemia index (RHI) was measured fasting to estimate endothelial function. Matsuda index was calculated from glucose and insulin concentrations collected fasting and 30 minutely for 2 h after a mixed meal (10 kcal/kg, 45% carbohydrate, 15% protein, 40% fat). The primary endpoint was the difference in RHI between low and high responders. RESULTS: There were no significant differences in age (61 ± 9 vs. 64 ± 7 years, p = .19), body mass index (BMI; 26 ± 3 vs. 24 ± 4 kg/m2 , p = .25) and sex (p = .71) between low and high responders. High responders had a lower RHI (2.1 ± 0.2 vs. 2.6 ± 0.2, p = .04) than low responders and there was a negative association between RHI and peak cortisol post ACTH1-24 (ß = -.56, p < .01). There were no significant differences in Matsuda index (15.0 ± 2.4 vs. 22.7 ± 5.2, p = .19) between high and low responders. CONCLUSION: In healthy adults, endothelial dysfunction is likely to contribute to the association between HPA hyperactivity and increased cardiovascular risk. As insulin sensitivity was not different in high and low responders, endothelial dysfunction is not primarily secondary to insulin resistance.

Insulin sensitivity, cardiovascular function and bone health in women with early stage breast cancer before and after cancer treatment.

BACKGROUND: Cardiovascular disease is a leading cause of death in breast cancer survivors, but the underlying cause is not fully characterised. AIMS: To determine whether insulin sensitivity, cardiovascular risk markers and body composition were perturbed in women treated with chemotherapy for early stage breast cancer and whether perturbations occurred before or after cancer treatment. METHODS: Sixteen women with breast cancer and 17 control subjects were studied. Twelve breast cancer patients returned for a second visit following cancer treatment comprising chemotherapy (n = 2), or chemotherapy and radiotherapy (n = 10). The Matsuda index to estimate insulin sensitivity, fasting lipids, pulse wave velocity (PWV), reactive hyperaemia index (RHI) and body composition by dual energy X-ray absorptiometry were measured. RESULTS: There were no significant differences in age (53 ± 9 vs 54 ± 11 years; P = 0.82) or body mass index (28 ± 7 vs 28 ± 6; P = 0.97) between patients with breast cancer and controls. Patients with breast cancer had higher triglycerides than controls (1.2 ± 0.1 vs 0.8 ± 0.1 mmol/L; P = 0.03), but there were no significant differences in the Matsuda index, PWV and RHI. Following cancer treatment, there was a lower Matsuda index (6.3 ± 1.2 vs 5.2 ± 1.0; P = 0.01), but this was not associated with a significant change in vascular function. Bone mass fell by 3% from 2.27 ± 0.11 to 2.20 ± 0.10 kg after cancer treatment (P = 0.03). CONCLUSIONS: Patients with breast cancer had higher triglycerides before treatment and a reduction in insulin sensitivity and bone mass following cancer treatment. Future larger and longer-term studies should characterise the effect of reduced insulin sensitivity on rates of diabetes, cardiovascular disease, cancer outcomes and fracture. TRIAL REGISTRATION: ACTRN12614001055695.

Treatment of prednisolone-induced hyperglycaemia in hospitalized patients: Insights from a randomized, controlled study.

AIM: Prednisolone causes hyperglycaemia predominantly between midday and midnight. Consequently, glargine-based basal-bolus insulin regimens may under treat daytime hyperglycaemia and cause nocturnal hypoglycaemia. We investigated whether an isophane-based insulin regimen is safer and more effective than a glargine-based regimen in hospitalized patients. MATERIALS AND METHODS: Fifty inpatients prescribed ≥20 mg/day prednisolone acutely with (1) finger prick blood glucose level (BGL) ≥15 mmol/L or (2) BGLs ≥10 mmol/L within the previous 24 hours were randomized to either insulin isophane or glargine before breakfast and insulin aspart before meals. The initial daily insulin dose was 0.5 U/kg bodyweight or 130% of the current daily insulin dose. Glycaemic control was assessed using a continuous glucose monitoring system. RESULTS: On Day 1, there were no significant differences in percentage of time outside a target glucose range of 4 to 10 mmol/L (41.3% ± 5.5% vs 50.0% ± 5.7%, P = .28), mean daily glucose (10.2 ± 0.7 vs 10.8 ± 0.8 mmol/L, P = .57) or glucose <4 mmol/L (2.2% ± 1.1% vs 2.0% ± 1.3%, P = .92) in patients randomized to isophane and glargine. In patients treated for 3 days, the prednisolone dose was reduced ( P = .02) and the insulin dose was increased over time ( P = .02), but the percentage of time outside the 4 to 10 mmol/L glucose range did not differ over time ( P = .45) or between groups ( P = .24). CONCLUSIONS: There were no differences in the efficacy or safety of the isophane and glargine-based insulin regimens. We recommend an initial daily insulin dose of 0.5 units/kg bodyweight if not on insulin, a greater than 30% increase in pre-prednisolone insulin dose and larger insulin dose adjustments in patients with prednisolone-induced hyperglycaemia.

Effects of prednisolone on energy and fat metabolism in patients with rheumatoid arthritis: tissue-specific insulin resistance with commonly used prednisolone doses.

OBJECTIVE: Glucocorticoids can cause postprandial hyperglycaemia, but the effects on postprandial energy and fat metabolism are uncertain. We investigated the effects of acute and chronic low-dose prednisolone on fasting and postprandial energy expenditure and substrate metabolism. DESIGN: An open interventional and cross-sectional study was undertaken. PATIENTS AND MEASUREMENTS: Eighteen patients who had not taken oral glucocorticoids for ≥6 months were studied before and after 7 days prednisolone (6 mg/day) to assess the acute effects of prednisolone. Baseline data from patients, not on glucocorticoids, were compared with 18 patients on long-term prednisolone (6·5 ± 1·8 mg/day for >6 months) to assess the chronic effects. Energy expenditure and substrate oxidation were measured using indirect calorimetry before and after a mixed meal. Adipocyte insulin resistance index and insulin-mediated suppression of NEFA were calculated from fasting and postprandial insulin and NEFA concentrations. RESULTS: There were no significant differences in resting energy expenditure or diet-induced thermogenesis with prednisolone. Acute (-2·1 ± 6·2 vs -16·3 ± 4·8 mg/min, P = 0·01) and chronic (-1·4 ± 2·8 vs -16·3 ± 4·8 mg/min, P = 0·01) prednisolone attenuated postprandial suppression of fat oxidation. Chronic (31·6 ± 3·8 vs 17·0 ± 3·3, P = 0·007), but not acute, prednisolone increased adipocyte insulin resistance index. However, insulin-mediated suppression of NEFA was not significantly different after acute or chronic prednisolone. CONCLUSIONS: Prednisolone does not alter energy expenditure. However, even at low doses, prednisolone exerts adverse effects on fat metabolism, which could exacerbate insulin resistance and increase cardiovascular risk. Attenuated postprandial suppression of fat oxidation, but not lipolysis, suggests that prednisolone causes greater insulin resistance in skeletal muscle than in adipocytes.

Effect of acute and chronic glucocorticoid therapy on insulin sensitivity and postprandial vascular function.

OBJECTIVE: Postprandial hyperglycaemia is associated with increased arterial stiffness and cardiovascular events. Low-dose prednisolone causes insulin resistance that typically manifests as postprandial hyperglycaemia. We investigated whether prednisolone causes postprandial vascular dysfunction in a cohort of patients with rheumatoid arthritis. DESIGN: An open interventional and cross-sectional study was undertaken. PATIENTS AND MEASUREMENTS: Eighteen subjects with rheumatoid arthritis who had not taken oral glucocorticoids for ≥6 months were studied before and after prednisolone 6 mg/day for 7 days to determine the acute effects of prednisolone. Pre-prednisolone data were compared to 18 subjects with rheumatoid arthritis taking long-term (>6 months) prednisolone (6·5 ± 1·8 mg/day) to assess the chronic effects of prednisolone. Augmentation index (by applanation tonometry) and reactive hyperaemia index (by peripheral artery tonometry) were measured before and after a mixed-meal (10 kcal/kg, 45% carbohydrate, 15% protein, 40% fat). Insulin sensitivity was estimated by the Matsuda index and sympathetic nervous system activity from urinary noradrenaline excretion. RESULTS: Matsuda index was lower after acute (2·0 ± 1·0 vs 3·6 ± 1·1, P = 0·01) and chronic (1·9 ± 1·0 vs 3·6 ± 1·1, P = 0·04) prednisolone. Postprandial augmentation index was lower after acute prednisolone (2551 ± 197 vs 2690 ± 272%*min, P ≤ 0·001), but not chronic prednisolone. There were no significant differences in reactive hyperaemia index with acute or chronic prednisolone. Noradrenaline excretion was lower after acute (54 ± 8 vs 93 ± 23 nmol/6 h, P = 0·02), but not chronic, prednisolone. CONCLUSIONS: Prednisolone-induced insulin resistance is not associated with postprandial vascular dysfunction in patients with rheumatoid arthritis. Reduced sympathetic activity may contribute to the reduction in postprandial arterial stiffness with acute prednisolone.

Low dose prednisolone and insulin sensitivity differentially affect arterial stiffness and endothelial function: An open interventional and cross-sectional study.

BACKGROUND AND AIMS: Glucocorticoids could impair vascular function directly, or indirectly by reducing insulin sensitivity. The aim of this study was to determine the direct and indirect effects of acute and chronic low dose prednisolone on arterial stiffness and endothelial function. METHODS: Twelve subjects with inflammatory arthritis, who had not taken oral glucocorticoids for ≥6 months, and 12 subjects with inflammatory arthritis, taking chronic (>6 months) low dose (6.3 ± 2.2 mg/day) prednisolone, were studied. Patients not on glucocorticoids underwent measurement of arterial stiffness (pulse wave velocity (PWV)) and endothelial function (reactive hyperaemia index (RHI)) before and after 7-10 days of prednisolone (6 mg/day), to assess the acute effects of prednisolone. Baseline data from patients not on glucocorticoids were compared with patients on long-term prednisolone to assess the chronic effects of prednisolone. Hepatic insulin sensitivity was estimated from percentage suppression of endogenous glucose production and peripheral insulin sensitivity as glucose infusion rate (M/I) during a hyperinsulinaemic-euglycaemic clamp. RESULTS: There were no significant changes in PWV with acute (9.2 ± 0.8 vs. 8.9 ± 0.8 m/sec, p = 0.33) or chronic (8.9 ± 0.8 vs. 9.0 ± 0.7 m/sec, p = 0.69) prednisolone. In multiple regression analysis, PWV was negatively associated with M/I during hyperinsulinemic-euglycemic clamp (p = 0.02), but not with suppression of endogenous glucose production (p = 0.15) or glucocorticoid use (p = 0.70). Chronic (2.4 ± 0.2 vs. 1.9 ± 0.1, p = 0.02), but not acute (1.8 ± 0.2 vs. 1.9 ± 0.1, p = 0.24), prednisolone resulted in a higher RHI. CONCLUSIONS: Arterial stiffness is not affected by low dose prednisolone per se, but is negatively associated with peripheral insulin sensitivity. Patients with rheumatoid arthritis taking long-term prednisolone had better endothelial function.

Opposing effects of rheumatoid arthritis and low dose prednisolone on arginine metabolomics.

BACKGROUND AND AIMS: The effects of low dose prednisolone on circulating markers of endothelial function, the arginine metabolites asymmetric dimethyl arginine (ADMA), mono methyl arginine (MMA), and homoarginine, are uncertain. We assessed whether patients with rheumatoid arthritis have perturbations in arginine metabolite concentrations that are reversed by low dose prednisolone. METHODS: Eighteen rheumatoid arthritis patients who had not taken prednisolone for >6 months (non-glucocorticoid (GC) users), 18 rheumatoid arthritis patients taking continuous oral prednisolone (6.5 ± 1.8 mg/day) for >6 months (GC users) and 20 healthy controls were studied. Fasting plasma concentrations of ADMA, MMA, and homoarginine were measured by ultra-performance liquid-chromatography. Baseline data from non-GC users were compared with healthy controls to assess the effect of rheumatoid arthritis. The change in arginine metabolites in non-GC users after 7 days of prednisolone (6 mg/day) was used to assess the acute effects of prednisolone. Baseline data from non-GC users were compared with GC users to assess the chronic effects of prednisolone. RESULTS: Non-GC users had higher ADMA (0.59 ± 0.03 vs. 0.47 ± 0.01 µM, p = 0.004) and MMA concentrations (0.10 ± 0.01 vs. 0.05 ± 0.00 µM, p < 0.001) than controls. The only change with acute prednisolone was a reduction in homoarginine (1.23 ± 0.06 vs. 1.08 ± 0.06 µM, p = 0.04) versus baseline. GC users had lower concentrations of ADMA (0.51 ± 0.02 vs. 0.59 ± 0.03 µM, p = 0.03) than non-GC users. CONCLUSIONS: Rheumatoid arthritis patients have higher concentrations of ADMA and MMA, inhibitors of endothelial function. Chronic, but not acute, prednisolone therapy is associated with a lower ADMA concentration, suggesting a salutary effect of long-term glucocorticoid treatment on endothelial function.

Relationship between Vitamin D Status and Autonomic Nervous System Activity.

Vitamin D deficiency is associated with increased arterial stiffness. However, the mechanisms underlying this association have not been clarified. The aim was to investigate whether changes in autonomic nervous system activity could underlie an association between 25 hydroxy vitamin D and arterial stiffness. A total of 49 subjects (age = 60 ± 8 years, body mass index = 26.7 ± 4.6 kg/m², 25 hydroxy vitamin D = 69 ± 22 nmol/L) underwent measurements of pulse wave velocity (PWV) and augmentation index (AIx), spontaneous baroreflex sensitivity, plasma metanephrines and 25 hydroxy vitamin D. Subjects with 25 hydroxy vitamin D ≤ 50 nmol/L were restudied after 200,000 International Units 25 hydroxy vitamin D. Plasma metanephrine was positively associated with AIx (p = 0.02) independent of age, sex, smoking and cholesterol and negatively associated with 25 hydroxy vitamin D (p = 0.002) independent of age, sex and season. In contrast, there was no association between baroreflex sensitivity and 25 hydroxy vitamin D (p = 0.54). Treatment with vitamin D increased 25 hydroxy vitamin D from 43 ± 5 to 96 ± 24 nmol/L (p < 0.0001) but there was no significant change in plasma metanephrine (115 ± 25 vs. 99 ± 39 pmol/L, p = 0.12). We conclude that as plasma metanephrine was negatively associated with 25 hydroxy vitamin D and positively with AIx, it could mediate an association between these two variables. This hypothesis should be tested in larger interventional studies.

Thrombospondin-1 is a glucocorticoid responsive protein in humans.

OBJECTIVE: Thrombospondin-1 (TSP1) is a matricellular protein whose gene expression has previously been shown to increase acutely after exposure to dexamethasone in vitro. The aim of this study was to determine if TSP1 is altered by acute and chronic states of glucocorticoid excess in human subjects. DESIGN AND METHODS: Three studies have been undertaken to assess the difference or change in TSP1 in response to altered glucocorticoid activity: i) an acute interventional study assessed the effects of a single 4 mg dose of dexamethasone in 20 healthy volunteers; ii) a cross-sectional study compared plasma TSP1 in 20 healthy volunteers and eight patients with Cushing's syndrome; iii) an interventional study assessed the effect on plasma TSP1 of an increase in hydrocortisone dose from ≤20 mg/day to 30 mg/day for 7 days in 16 patients with secondary adrenal insufficiency. RESULTS: In healthy volunteers, 4 mg dexamethasone significantly increased peripheral blood mononuclear cell (PBMC) TSP1 mRNA levels (P<0.0001) and plasma TSP1 concentrations (P<0.0001), peaking at 12 h. Median (interquartile range) plasma TSP1 was higher in Cushing's, 638 (535-756) ng/ml, than in healthy volunteers, 272 (237-336) ng/ml (P<0.0001). Plasma TSP1 >400 ng/ml diagnosed Cushing's syndrome with sensitivity of 100% and specificity of 85%. The higher hydrocortisone dose increased plasma TSP1 from 139 (86-199) to 256 (133-516) ng/ml, (P<0.01) in patients with secondary adrenal insufficiency. CONCLUSIONS: TSP1 is a glucocorticoid responsive protein in humans. Further research is required to determine if plasma TSP1 has a role as a glucocorticoid biomarker.

Acute effect of increasing glucocorticoid replacement dose on cardiovascular risk and insulin sensitivity in patients with adrenocorticotrophin deficiency.

CONTEXT: Higher hydrocortisone doses are associated with increased overall and cardiovascular mortality in ACTH-deficient patients. The mechanisms underlying this association have not been fully defined. OBJECTIVE: The aim of the study was to determine whether increasing hydrocortisone (or equivalent) to 30 mg/d in ACTH-deficient patients increased cardiovascular risk and whether a reduction in insulin sensitivity and attenuation of insulin's hemodynamic effects was responsible for this effect. DESIGN: We conducted an open interventional study between 2011 and 2013. SETTING: The study was performed in the Endocrine Research Unit, Repatriation General Hospital, Adelaide, Australia. PATIENTS: Seventeen ACTH-deficient subjects taking hydrocortisone (≤20 mg/d) for at least 6 months were studied. INTERVENTION: Subjects were studied before and after a 7-day increase in hydrocortisone to 30 mg/d. MAIN OUTCOME MEASURE: The primary outcome was the change in pulse wave velocity, both fasting and after a 75-g oral glucose load. RESULTS: Fasting and post-glucose load pulse wave velocities were not significantly different on the higher glucocorticoid dose. Fasting augmentation index (24.9 ± 2.7 vs 22.6 ± 2.6%; P = .04) and reactive hyperemia index (2.3 ± 0.2 vs 2.0 ± 0.2; P = 0.04) were lower on the higher glucocorticoid dose, with no significant difference in the post-glucose load changes in these variables. There were no significant changes in insulin sensitivity or secretion on the higher glucocorticoid dose. CONCLUSIONS: Endothelial dysfunction may contribute to the increased cardiovascular mortality associated with higher glucocorticoid doses. This may be a direct glucocorticoid effect, not mediated by insulin resistance. ACTH-deficient patients should thus be prescribed the lowest safe glucocorticoid replacement dose.

Acute effect of calcium citrate on serum calcium and cardiovascular function.

Calcium supplements have been associated with an increased risk of cardiovascular events. However, the validity of these findings has been questioned. A major concern is that the mechanism underlying an increase in cardiovascular events has not been demonstrated. Calcium initiates cardiac and vascular contraction following influx of calcium into cardiac and smooth muscle from extracellular fluid. We have investigated whether the acute rise in serum calcium following calcium supplement administration is associated with adverse changes in cardiovascular function. In an open interventional study, we recruited 25 volunteers (16 female, age 60.3 ± 6.5 years, body mass index 25.7 ± 2.7 kg/m2) from the community who were not taking calcium supplements. Participants were studied before and 3 hours after a single oral dose of 1000 mg calcium citrate. We assessed well-validated markers of arterial stiffness (pulse wave velocity [PWV]), arterial wave reflection (augmentation index [AIx]), and myocardial perfusion (subendocardial viability ratio [SEVR]) by pulse wave analysis and endothelial function (reactive hyperemia index [RHI]) by peripheral arterial tonometry. Total and ionized serum calcium were acutely increased by 0.10 ± 0.07 and 0.06 ± 0.03 mmol/L, respectively, 3 hours after calcium citrate administration (p < 0.0001 for both comparisons). Following administration of calcium citrate there was a fall in AIx from a median of 29.7% (23.8% to 34.0%) to 26.4% (22.7% to 34.0%, p = 0.03) and an increase in SEVR from 163% (148% to 174%) to 170% (149% to 185%, p = 0.007). PWV and RHI were not significantly altered. The change in total calcium was negatively correlated with the change in AIx (r = -0.48, p = 0.02). In summary, the acute increase in serum calcium following calcium supplement administration is associated with reduced arterial wave reflection and a marker of increased myocardial perfusion. If maintained long-term, these changes would be expected to reduce cardiovascular risk. Acute serum calcium-mediated changes in these parameters of cardiovascular function are unlikely to underlie an association between calcium supplementation and cardiovascular events.

Effects of low-dose prednisolone on hepatic and peripheral insulin sensitivity, insulin secretion, and abdominal adiposity in patients with inflammatory rheumatologic disease.

OBJECTIVE: The metabolic effects of low-dose prednisolone and optimal management of glucocorticoid-induced diabetes are poorly characterized. The aims were to investigate the acute effects of low-dose prednisolone on carbohydrate metabolism and whether long-term low-dose prednisolone administration increases visceral adiposity, amplifying metabolic perturbations. RESEARCH DESIGN AND METHODS: Subjects with inflammatory rheumatologic disease without diabetes mellitus were recruited. Nine subjects (age, 59 ± 11 years) not using oral glucocorticoids were studied before and after a 7- to 10-day course of oral prednisolone 6 mg daily. Baseline data were compared with 12 subjects (age, 61 ± 8 years) using continuous long-term prednisolone (6.3 ± 2.2 mg/day). Basal endogenous glucose production (EGP) was estimated by 6,6-(2)H2 glucose infusion, insulin sensitivity was estimated by two-step hyperinsulinemic-euglycemic clamp, insulin secretion was estimated by intravenous glucose tolerance test, and adipose tissue areas were estimated by computed tomography. RESULTS: Prednisolone acutely increased basal EGP (2.44 ± 0.46 to 2.65 ± 0.35 mg/min/kg; P = 0.05) and reduced insulin suppression of EGP (79 ± 7 to 67 ± 14%; P = 0.03), peripheral glucose disposal (8.2 ± 2.4 to 7.0 ± 1.6 mg/kg/min; P = 0.01), and first-phase (5.9 ± 2.0 to 3.9 ± 1.6 mU/mmol; P = 0.01) and second-phase (4.6 ± 1.7 to 3.6 ± 1.4 mU/mmol; P = 0.02) insulin secretion. Long-term prednisolone users had attenuated insulin suppression of EGP (66 ± 14 vs. 79 ± 7%; P = 0.03) and nonoxidative glucose disposal (44 ± 24 vs. 62 ± 8%; P = 0.02) compared with nonglucocorticoid users, whereas basal EGP, insulin secretion, and adipose tissue areas were not significantly different. CONCLUSIONS: Low-dose prednisolone acutely perturbs all aspects of carbohydrate metabolism. Long-term low-dose prednisolone induces hepatic insulin resistance and reduces peripheral nonoxidative glucose disposal. We conclude that hepatic and peripheral insulin sensitivity should be targeted by glucose-lowering therapy for glucocorticoid-induced diabetes.

Free and total plasma cortisol measured by immunoassay and mass spectrometry following ACTH1₋24 stimulation in the assessment of pituitary patients.

CONTEXT: Measurement of plasma cortisol by immunoassay after ACTH1₋24 stimulation is used to assess the hypothalamic-pituitary-adrenal (HPA) axis. Liquid chromatography-tandem mass spectrometry (LCMS) has greater analytical specificity than immunoassay and equilibrium dialysis allows measurement of free plasma cortisol. OBJECTIVE: We investigated the use of measuring total and free plasma cortisol by LCMS and total cortisol by immunoassay during an ACTH1₋24 stimulation test to define HPA status in pituitary patients. DESIGN AND SETTING: This was a case control study conducted in a clinical research facility. PARTICIPANTS: We studied 60 controls and 21 patients with pituitary disease in whom HPA sufficiency (n = 8) or deficiency (n = 13) had been previously defined. INTERVENTION: Participants underwent 1 µg ACTH(1-24) intravenous and 250 µg ACTH1₋24 intramuscular ACTH1₋24 stimulation tests. MAIN OUTCOME MEASURES: Concordance of ACTH1₋24-stimulated total and free plasma cortisol with previous HPA assessment. RESULTS: Total cortisol was 12% lower when measured by immunoassay than by LCMS. Female sex and older age were positively correlated with ACTH1₋24-stimulated total and free cortisol, respectively. Measurements of total cortisol by immunoassay and LCMS and free cortisol 30 minutes after 1 µg and 30 and 60 minutes after 250 µg ACTH1₋24 were concordant with previous HPA axis assessment in most pituitary patients. However, free cortisol had greater separation from the diagnostic cutoff than total cortisol. CONCLUSIONS: Categorization of HPA status by immunoassay and LCMS after ACTH1₋24 stimulation was concordant with previous assessment in most pituitary patients. Free cortisol may have greater clinical use in patients near the diagnostic threshold.