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

Investigation of the Hypothalamo-pituitary-adrenal (HPA) axis: a contemporary synthesis

The hypothalamo-pituitary-adrenal (HPA) axis is one of the main components of the stress system. Maintenance of normal physiological events, which include stress responses to internal or external stimuli in the body, depends on appropriate HPA axis function. In the case of severe cortisol deficiency, especially when there is a triggering factor, the patient may develop a life-threatening adrenal crisis which may result in death unless early diagnosis and adequate treatment are carried out. The maintenance of normal physiology and survival depend upon a sufficient level of cortisol in the circulation. Life-long glucocorticoid replacement therapy, in most cases meeting but not exceeding the need of the patient, is essential for normal life expectancy and maintenance of the quality of life. To enable this, the initial step should be the correct diagnosis of adrenal insufficiency (AI) which requires careful evaluation of the HPA axis, a highly dynamic endocrine system. The diagnosis of AI in patients with frank manifestations is not challenging. These patients do not need dynamic tests, and basal cortisol is usually enough to give a correct diagnosis. However, most cases of secondary adrenal insufficiency (SAI) take place in a gray zone when clinical manifestations are mild. In this situation, more complicated methods that can simulate the response of the HPA axis to a major stress are required. Numerous studies in the assessment of HPA axis have been published in the world literature. In this review, the tests used in the diagnosis of secondary AI or in the investigation of suspected HPA axis insufficiency are discussed in detail, and in the light of this, various recommendations are made.

Cosyntropin-Stimulated Serum Free Cortisol in Healthy, Adrenally Insufficient, and Mildly Cirrhotic Populations

CONTEXT

Serum free cortisol (SFF) responses to cosyntropin simulation test (CST) may more accurately assess adrenal function than total cortisol (TF).

OBJECTIVE

The objective of the study was to evaluate the diagnostic utility of SFF responses during a 250-μg CST.

DESIGN

We recruited healthy volunteers (HV; n = 27), patients with primary and secondary adrenal insufficiency (n = 19 and n = 24, respectively), and subjects with Child-Pugh class A cirrhosis (CH; n = 15). Each received 250 μg cosyntropin with measurement of ACTH and corticosteroid binding globulin (CBG) at time 0 and TF and SFF at 0, 30, and 60 minutes. Salivary cortisol was measured at all time points in CH subjects.

RESULTS

Peak SFF and TF were significantly higher in HVs vs both AI groups (P < .05). Peak SFF and TF (6.8 μg/dL vs 2.2 μg/dL; [188 nmol/L vs 62 nmol/L]; P < .01) were significantly higher in the secondary adrenal insufficiency vs primary adrenal insufficiency patients. The optimal peak SFF criterion to identify adrenal insufficiency patients vs HV was 0.9 μg/dL (25 nmol/L) (sensitivity of 95%, specificity of 100%). Mean CBG and albumin levels were similar among all four groups. CH patients had a higher peak SFF than HV (2.4 vs 2.0 μg/dL; P = .02. In the CH patients, peak salivary cortisol levels correlated well with peak SFF (rs = 0.84, P = .005). CBG levels were similar among the groups.

CONCLUSION

We provide normative data for SFF values in HV and AI during the CST. Normal CBG levels in mild cirrhosis did not affect the interpretation of the CST.