Serum free cortisol as an ancillary tool in the interpretation of the low-dose 1-μg ACTH test

Gender-affirming hormone therapy effect on cortisol levels in trans males and trans females

PURPOSE

Previous studies have shown differences in baseline and stimulated cortisol levels between men and women. Whether this difference is secondary to sex hormones or to other factors, such as genetic or epigenetic changes, is unknown. We investigated the effect of gender-affirming hormone treatment (GAHT) on the hypothalamo-pituitary-adrenal axis of transgender subjects in an effort to throw light on this question.

METHODS

Ten transgender males (TM) and eight transgender females (TF) underwent a low-dose (1 µg) adrenocorticotropic hormone (ACTH) stimulation test before and 6 months after GAHT initiation. Serum total, free and salivary cortisol (SC) levels were measured at baseline and at 20, 30 and 40 min.

RESULTS

For the TM, all three levels were significantly lower at several time points after ACTH injection compared to pretreatment levels following 6 months of treatment (p < .05). Likewise, the overall SC response as calculated by the area under the curve was significantly lower (p = .0053). For the TF, the basal total cortisol (TC) level increased after 6 months of treatment (p < .01) while ACTH-stimulated SC levels decreased significantly. The basal ACTH levels were significantly lower following hormonal therapy (p < .001).

CONCLUSION

Stimulated salivary cortisol levels decreased significantly after 6 months of GAHT in both male and female transgender subjects, possibly reflecting a decreased state of anxiety associated with treatment initiation. Additionally, basal and stimulated serum TC levels increased after hormonal treatment in the TF, probably secondary to the effect of oestrogen on cortisol-binding globulin.

The free cortisol calculated: correlation with the free cortisol concentrations measured with liquid chromatography-tandem mass spectrometry after equilibrium dialysis and establishment of reference intervals

BACKGROUND

Changes in cortisol binding globulin (CBG) impact the total serum cortisol concentration and affect the accurate assessment of adrenal function. Free biologically cortisol can be calculated using different equations or directly measured after complicated procedures.

METHODS

The free cortisol index (FCI) obtained using the Bonte formula as well as the free cortisol concentration calculated (Coolens equation) were first estimated for 45 healthy workers. The CBG level was determined by a competitive radioimmunoassay and the total cortisol concentration, was measured with an electrochemiluminescent assay. The correlations between FCI, the free cortisol concentrations calculated and the free cortisol levels measured with liquid chromatography-tandem mass spectrometry after equilibrium dialysis were studied for those 45 samples. Reference limits were established on 158 healthy hospital workers and patients with serum samples collected between 7:30 am and 10 am.

RESULTS

The FCI as well as the free cortisol concentrations calculated obtained for the 45 samples correlated significantly with the free cortisol levels measured. Although the cortisol and CBG levels were statistically higher in women using contraceptives compared with women not taking them as well as men, the calculated FCI and free cortisol concentrations did not differ between these groups. The medians (P2.5-P97.5) obtained for the 158 healthy workers were respectively 26.4% (12.3-51.6%) and 10.6 nmol/L (4.3-26.7 nmol/L).

CONCLUSIONS

This study highlighted a significant correlation between the FCI, the free cortisol concentrations calculated and the free cortisol levels measured with LC-MS/MS, it has also allowed the establishment of reference intervals for calculated FCI and free cortisol.

The Low-Dose ACTH Test: Usefulness of Combined Analysis of Serum and Salivary Maximum Cortisol Response in Pediatrics

CONTEXT

The low-dose (1 µg) ACTH test (LDT) is widely used to assess central adrenal insufficiency (CAI); however, the serum cortisol cutoff value is controversial. Salivary cortisol (SC) may be a more accurate measurement for CAI.

OBJECTIVE

To assess a new maximum cutoff value of serum cortisol after LDT in pediatric patients, taking into account serum and SC measurements.

DESIGN AND SETTING

Prospective study in a pediatric tertiary referral center.

WORKING HYPOTHESIS

The combined analysis of serum and SC response to LDT might improve LDT for CAI diagnosis.

PARTICIPANT AND OUTCOME MEASUREMENT

A total of 145 pediatric patients underwent LDT. Serum and SC levels were measured. A central adrenal sufficient (CAS) response was established according to the reference serum cortisol cutoff value of ≥497 nmol/L.

RESULTS

The LDT study showed central adrenal sufficiency in 72 patients and CAI in 73 patients. Considering the lower quartile of maximum SC value (21 nmol/L) in the CAS group, an intermediate CAI (InCAI) group and a real CAI (RCAI) group were defined. Regarding the median maximum value of serum cortisol levels in the InCAI group, a new serum cortisol cutoff value of 450 nmol/L was established. Furthermore, 91% of the patients in the RCAI group were below this cutoff value.

CONCLUSION

The combined evaluation of maximum serum and SC levels to LDT might be useful to define an InCAI group and to avoid unnecessary hormone replacement therapy. However, rigorous patient follow-up is required.

SERUM FREE CORTISOL DURING GLUCAGON STIMULATION TEST IN HEALTHY SHORT-STATURED CHILDREN AND ADOLESCENTS

OBJECTIVE

The total cortisol (TC) response may be measured during the glucagon stimulation test (GST) for growth hormone (GH) reserve in order to assess the integrity of the hypothalamic-pituitary-adrenal (HPA) axis. Measurements of TC are unreliable in conditions of albumin and cortisol-binding globulin (CBG) alterations (e.g., hypoproteinemia or CBG deficiency). We aimed to measure the serum free cortisol (sFC) response to the GST in children and adolescents and determine whether it could predict the GH response to glucagon stimulation.

METHODS

Infants and children with either short stature or growth attenuation who were referred for evaluation of GH reserve underwent the GST.

RESULTS

The study population consisted of 103 subjects (62 females), median age 3.9 years (range, 0.5-14). The mean basal and peak TC levels were 13.3 ± 6.7 μg/dL and 29.6 ± 8.8 μg/dL, respectively. The mean basal and peak sFC levels were 0.7 ± 0.8 μg/dL and 1.7 ± 1.1 μg/dL, respectively. There was a negative correlation between peak TC and age ( r = -0.3, P = .007) but not between peak sFC and age ( r = -0.09, P = .36). Ninety-five percent of the patients had peak TC levels >15.8 μg/dL and peak sFC levels >0.6 μg/dL.

CONCLUSION

Our results on a cohort of healthy short-statured children can serve as reference values for the sFC response during GST. Based on these results, we propose peak TC levels >15.8 μg/dL and peak sFC levels >0.6 μg/dL for defining normalcy of the HPA axis during the GST in children and adolescents.

ABBREVIATIONS

ACTH = adrenocorticotrophic hormone BMI = body mass index CBG = cortisol-binding globulin GH = growth hormone GST = glucagon stimulation test HPA = hypothalamic-pituitary-adrenal SDS = standard deviation score sFC = serum free cortisol TC = total cortisol.

Characterization of the serum and salivary cortisol response to the intravenous 250 µg ACTH1-24 stimulation test

PURPOSE

The ACTH_1-24 stimulation test is commonly used to assess the hypothalamic-pituitary-adrenal (HPA) axis. Given variations in CBG concentration and binding affinity, serum total cortisol may misclassify some patients. Salivary cortisol correlates well with serum free cortisol but is easier to measure and widely available in commercial laboratories. The aim of this study was to investigate the utility of measuring salivary cortisol during the ACTH_1-24 stimulation test.

DESIGN AND METHODS

Case-control study in a clinical research facility. Eighty-seven patients with suspected cortisol deficiency, twenty-four healthy controls, and ten healthy women on the oral contraceptive (OC) underwent an intravenous 250 µg ACTH_1-24 stimulation test. Concordance of ACTH_1-24 stimulated serum and salivary cortisol was evaluated.

RESULTS

There was a significant difference in serum cortisol between the healthy volunteers and the women on the OC (P < 0.001) but no difference in salivary cortisol. The lower limit of the reference interval for salivary cortisol at 60 min was 26 nmol/L. 27/89 (30%) of tests with suspected HPA axis disorder failed the 60 min serum cortisol cut-off of 500 nmol/L. Of these, 24/27 (89%) had a salivary cortisol of <26 nmol/L. In contrast, 12/19 (63%) tests and 5/43 (12%) tests where the 60 min serum cortisol was 500-599 and ≥600 nmol/L, respectively had a salivary cortisol of <26 nmol/L.

CONCLUSIONS

Salivary cortisol provides additional diagnostic value during the 250 µg ACTH_1-24 stimulation test in patients with proven or suspected alterations in CBG and potentially those with a borderline 60 min serum cortisol 500-599 nmol/L.

The role of corticosteroid-binding globulin in the evaluation of adrenal insufficiency

Cortisol is a hydrophobic molecule that is largely bound to corticosteroid-binding globulin (CBG) in the circulation. In the assessment of adrenal insufficiency, many clinicians measure a total serum cortisol level, which assumes that CBG is present in normal concentrations and with a normal binding affinity for cortisol. CBG concentration and affinity are affected by a number of common factors including oral contraceptive pills (OCPs), fever and infection, as well as rare mutations in the serine protease inhibitor A6 (SERPINA6) gene, and as such, total cortisol levels might not be the ideal way to assess adrenal function in all clinical circumstances. This paper reviews the limitations of immunoassay and liquid chromatography-tandem mass spectrometry (LC-MS/MS) in the measurement of total cortisol, the challenges of measuring free serum cortisol directly as well as the difficulties in calculating an estimated free cortisol from total cortisol, CBG and albumin concentrations. Newer approaches to the evaluation of adrenal insufficiency, including the measurement of cortisol and cortisone in the saliva, are discussed and a possible future role for these tests is proposed.

Establishing Normal Ranges of Basal and ACTH-Stimulated Serum Free Cortisol in Children

BACKGROUND

Normative data have been established for stimulated serum total cortisol in children but not for serum free cortisol.

METHODS

Children who were referred for ACTH testing to rule out adrenal insufficiency were enrolled. Only children with normal response and normal androgen levels were included. Total cortisol was determined by a chemiluminescence method, and free cortisol was measured by the same method following equilibrium dialysis.

RESULTS

The study group consisted of 85 subjects (28 male; 57 female) with a median age of 8.5 years (range 0.6-17.7). The mean basal and peak total cortisol levels were 11.5 ± 5.7 and 32.9 ± 6.2 μg/dl, respectively. The mean basal and peak free cortisol levels were 0.4 ± 0.3 and 1.8 ± 0.6 μg/dl, respectively. There was a negative correlation between peak total cortisol and age but not between peak free cortisol and age. The 3rd and 97th percentile values for peak free cortisol were 0.94 μg/dl (26 nmol/l) and 2.97 μg/dl (82 nmol/l), respectively.

CONCLUSIONS

Measurement of free cortisol has the advantage of being independent of cortisol-binding globulin levels. This study provides reference ranges for stimulated free cortisol in children, with a cutoff value of 0.9 μg/dl (25 nmol/l) as a normal response to a standard ACTH test.

Salivary Cortisol and Cortisone After Low-Dose Corticotropin Stimulation in the Diagnosis of Adrenal Insufficiency

Context:

Basal and poststimulation salivary cortisol and cortisone levels can be useful in the diagnosis of adrenal insufficiency. However, little is known about the optimal cutoffs and performance characteristics of these tests.

Objective:

To derive the cutoff values and study the performance characteristics of salivary cortisol and salivary cortisone in the diagnosis of adrenal insufficiency.

Design and Setting:

Prospective study in a regional hospital in Hong Kong from January 2014 to September 2015.

Participants:

Fifty-six Chinese healthy volunteers and 171 patients suspected of having adrenal insufficiency.

Main Outcome Measures:

All participants underwent low-dose short Synacthen test (LDSST) with intravenous injection of 1 μg of tetracosactide (Synacthen 1–24). Serum cortisol, salivary cortisol and cortisone levels were measured at baseline and 30 and 60 minutes afterward.

Results:

Using the reference cutoff (mean − 2 standard deviations of post-LDSST peak serum cortisol) derived from healthy volunteers as the gold standard, receiver operating characteristic analysis of patients’ data revealed that both post-LDSST peak salivary cortisol and cortisone performed better than basal tests. The most optimal cutoff values for serum cortisol as measured by immunoassay and for salivary cortisol and salivary cortisone as measured by liquid chromatography–tandem mass spectrometry (LC-MS/MS) were 376, 8.6, and 33.5 nmol/L, respectively, for post-LDSST peak values, and 170, 1.7, and 12.5 nmol/L, respectively, for basal values.

Conclusions:

We established method-specific reference cutoffs for serum cortisol, salivary cortisol, and salivary cortisone during LDSST. Both post-LDSST peak salivary cortisol and cortisone performed well as diagnostic tests for adrenal insufficiency. Their measurements by LC-MS/MS can alleviate problems associated with serum cortisol immunoassays.

GENDER DETERMINES SERUM FREE CORTISOL: HIGHER LEVELS IN MEN

OBJECTIVE

Because only the free fraction of serum cortisol can readily access glucocorticoid receptors, we investigated whether or not a gender-related difference in serum free cortisol (FC) exists in the basal and adrenocorticotropic hormone (ACTH)-stimulated state.

METHODS

Serum total cortisol (TC) and FC were measured in 323 subjects (175 men; 148 women). Additionally, the low-dose 1-μg ACTH test was performed in 56 subjects (30 women, 26 men). Subjects were healthy volunteers, recruited in a preventive medicine screening program and an outpatient clinic.

RESULTS

Overall, basal serum TC and FC level were ~18 and ~33%, respectively, higher in men than in women (TC, 14.5 ± 0.33 μg/dL vs. 12.3 ± 0.33 μg/dL; P<.0001; FC, 0.68 ± 0.02 μg/dL vs. 0.51 ± 0.02 μg/dL; P<.0001). The higher FC in men relative to women was apparent across a wide age range (17 to 86 years) and persisted after adjustment for age and body mass index. The FC fraction (%FC, out of TC) was concordantly higher in men (5.4 ± 0.09% vs. 4.8 ± 0.3%; P = .046). FC was not related to the estimated menopausal status (women age below and above 47, 50, or 53 years). ACTH-stimulated FC levels were significantly higher in men compared to women, as reflected by the area under the response curve (49.4 ± 3.4 μg × min vs. 39.6 ± 2.2 μg × min; P = .0014).

CONCLUSION

Gender is an unrecognized determinant of serum FC in humans. The possibility of lifelong exposure to the higher bioactive fraction of cortisol under basal conditions or daily stress involving ACTH stimulation should be further investigated in the context of gender-related phenotypic features such as "android" (visceral) fat deposition and longevity.

ABBREVIATIONS

ACTH = adrenocorticotropic hormone BMI = body mass index CBG = cortisol-binding globulin FC = free cortisol HPA = hypothalamic-pituitary-adrenal TC = total cortisol.

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.

Comparison of total cortisol, free cortisol, and surrogate markers of free cortisol in diagnosis of adrenal insufficiency in patients with stable cirrhosis

BACKGROUND & AIMS

Measurements of serum levels of total cortisol can overestimate the prevalence of adrenal dysfunction in patients with cirrhosis because they have low concentrations of corticosteroid-binding globulin and albumin. We used measurements of serum total cortisol and serum free cortisol after the low-dose short Synacthen test (LDSST) to assess adrenal dysfunction.

METHODS

We studied 79 patients with stable cirrhosis; adrenal dysfunction was defined by peak concentrations of total cortisol ≤494 mmol/L and/or peak concentrations of free cortisol ≤33 nmol/L after the LDSST. We determined free cortisol index (FCI) scores and calculated free cortisol levels by using Coolens' equation. The Cox regression model was used to assess the relationship between adrenal dysfunction and outcomes (death or liver transplant).

RESULTS

On the basis of measurement of total cortisol, 34% of patients had adrenal dysfunction, and on the basis of measurement of free cortisol, 29% had adrenal dysfunction. There was agreement between total cortisol and free cortisol levels in 22% of patients; in 13%, adrenal dysfunction was diagnosed only on the basis of total cortisol and in 6% only on the basis of free cortisol (κ coefficient, 0.56; P < .01). Low concentrations of corticosteroid-binding globulin (21 vs 54 μg/mL, P < .01) led to an overestimation of adrenal dysfunction that was based on measurement of total cortisol. Measurements of calculated free cortisol constantly overestimated free cortisol concentrations, with variations as large as 87% for baseline values and up to 84% after stimulation. Adrenal insufficiency, defined by FCI scores <12, was detected in 30% of patients; among them, 23% also had subnormal peak levels of free cortisol (κ coefficient, 0.70; P < .001). Adrenal dysfunction was not significantly associated with patient outcomes, on the basis of Cox model analysis.

CONCLUSIONS

Adrenal insufficiency, defined by LDSST, is frequent in patients with stable cirrhosis, on the basis of measurements of total and free cortisol. FCI scores are better than measurement of total cortisol in assessing adrenal function in patients with cirrhosis. We did not associate adrenal dysfunction with outcome, but further studies are needed.

Serum cortisol seems to be a more appropriate marker for adrenocortical reserve evaluation in ACTH test in comparison to salivary cortisol

Salivary cortisol reflects the free fraction of serum cortisol. Monitoring salivary cortisol may be a promising alternative method for assessing serum cortisol in some clinical situations. We aimed to compare the reliability of salivary vs. serum cortisol during ACTH test. 84 subjects (mean age 63.2; 24-89 years; n=66 males) suspected for adrenocortical insufficiency underwent an ACTH test. Patients were divided based on peak serum cortisol into hypocortical group with cortisol <500 nmol/l and to reference group cortisol >500 nmol/l. Median serum cortisol levels in reference group were 445, 766, and 902 nmol/l at 0, 30, and 60 minutes, respectively, and in hypocortical group were 256, 394, and 453 nmol/l. Median salivary cortisol levels were 19.02, 40.02, and 62.1 nmol/l in reference group, and 9.60, 14.08, and 13.28 nmol/l in hypocortical group. Obtained values showed good correlation between serum and salivary cortisol (p<0.0001). The percentage of explained variability R(2) (coefficient of determination for linear model) representing a measure of agreement between experimental values and predictions for repeated measures ANOVA, was significantly higher (p=0.021) for serum cortisol (R2=93.4 %) when compared to the salivary cortisol (R2=89.3 %). A stronger discriminating power of serum versus salivary cortisol suggests that it seems to be slightly, but statistically significantly more appropriate marker of adrenocortical reserve in ACTH test.