[The glucagon test in diagnosis of secondary adrenal insufficiency after craniospinal irradiation: the feasibility of application, the features of performing the test, and its diagnostic informativity]

ACTH Stimulation Test for the Diagnosis of Secondary Adrenal Insufficiency: Light and Shadow

Secondary Adrenal Insufficiency (SAI) is a condition characterized by inappropriately low ACTH secretion due to a disease or injury to the hypothalamus or the pituitary. The evaluation when suspected is often challenging for the non-specific symptoms, the rarity of the disease, and the pitfalls associated with laboratory tests. A prompt and correct diagnosis of SAI is essential because although an adequate hormonal replacement therapy could be lifesaving, inappropriate life-long therapy with steroids can be harmful. The gold standard test for assessing the hypothalamus-pituitary-adrenal axis (HPA) is the insulin tolerance test (ITT), but due to safety issues is not widely used. Conversely, the ACTH stimulation test is a safer and well-tolerated tool for SAI diagnosis. However, data about its diagnostic accuracy show great variability due to both technical and interpretative aspects, such as dose, route of administration, the timing of the test, and assay used for cortisol measurements. Consequently, the clinical background of the patient and the pretest probability of HPA axis impairment become of paramount importance. We aimed to summarize the recent literature evidence in the conduction and interpretation of the ACTH stimulation test for the diagnosis of SAI to provide updated insights on its correct use in clinical practice.

[Comparative study of glucagon and insulin tests for diagnostics of secondary adrenal insufficiency and growth hormone deficiency in children and adolescents]

BACKGROUND

Diagnostics of growth hormone deficiency (GHD) and secondary adrenal insufficiency (SAI) is based on estimation of peak GH and cortisol concentrations in provocation tests. Russian consensus on diagnostics and treatment of hypopituitarism in children and adolescences recommends to measure GH and cortisol concentrations in every time-point of insulin test (IT). Glucagon test (GT) is discussed in literature as alternative to IT.

AIMS

To estimate the possibility to use provocation GT for diagnostics of SAI and GHD in children and adolescents.

MATERIALS AND METHODS

We investigated blood and urine cortisol levels, IT, and GT in 20 patients 6.5-17.8 years (Me 13.0 (10.4; 15.3)) after surgery and/or radiology and/or chemical therapy of head and neck tumors; remission for 0.4-7.5 years (Ме 2.1 (1.5; 5.2)).

RESULTS

With cut-off point 550 nmol/L sensitivity and specifity of IT was 100% and 60%, GT - 100% and 53% respectively. Minimal cortisol cut-off level for GT with sensitivity 100% was 500 nmol/L, maximal with specifity 100% - 400 nmol/L.Early morning cortisol levels did not exceed 250 nmol/l in 2 patients with SAI; and were above 500 nmol/l in 8 patients without SAI while primary or repeated examination.GHD was reviled by IT in all patients. Maximal GH concentrations in GT and IT did not differ significantly (p>0.05) but GT results of 4 patients exceeded or met cut-off for this test (7 ng/ml).GT was characterized by less severity compared with IT.

CONCLUSIONS

For diagnostics of SAI by GT we can advise cut-off points of cortisol level 500 (sensitivity 100%, specifty 53%) and 400 nmol/L (sensitivity 80%, specifity 100%). Measuring of cortisol levels in 2-3 early morning blood samples allows to exclude or to suspect SAI in half of patients before tests. GH peaks in GT can exceed similarly data in IT that needs future investigation.