Criteria for distinguishing normal and subnormal adrenocortical function using the Synacthen test

Abstract

SummaryThe Synacthen test consists of the measurement of plasma corticosteroid concentrations by a fluorimetric method before (basal) and 30 min after a single intramuscular administration of 250 Vg of tetracosactrin (Synacthen), a synthetic polypeptide with ACTH activity equivalent to that of natural corticotrophin.In a control group of forty-five subjects the basal plasma corticosteroid level was not lower than 6 tig/ 100 ml (a lower limit of 5 ,tg/100 ml is accepted in the afternoon and evening), the increment was not less than 7 tg/100 ml and the plasma corticosteroid concentration after Synacthen was not less than 18 ,ug/100 ml. From these results the '6 (5), 7, 18' rule was formulated and any patient who failed to satisfy at least two of these criteria was considered to have adrenocortical insufficiency.

Experience with the use of a corticosteroid aerosol.

“…Adrenal function was tested in these three studies, and no significant impairment of adrenal function was detected on increasing the d\ose to 800 gg daily. Although Gaddie et al (1973) noted a smaller incremental increase in the response to a tetracosactrin challenge at 1600 tg daily, the test was well within the defined normal limits (Greig et al, 1969).…”

Two Cases of Asymptomatic Adrenocortical Insufficiency with Autoimmune Thyroid Disease.

“…Our two cases had low or low normal cortisol level and increased ACTH, and had a subnormal response to rapid ACTH test. There has been controversy about the criteria for normal adrenal function in rapid ACTH test [3,5,6]. It was earlier reported that the basal plasma corticosteroid concentration, measured by fluorimetric assay, is not less than 6 ,ug/dl, the increase is not less than 7 ,ag/dl, and the concentration following stimulation is not less than 18 jig/dl ("6, 7, 18 rule") [5].…”

“…There has been controversy about the criteria for normal adrenal function in rapid ACTH test [3,5,6]. It was earlier reported that the basal plasma corticosteroid concentration, measured by fluorimetric assay, is not less than 6 ,ug/dl, the increase is not less than 7 ,ag/dl, and the concentration following stimulation is not less than 18 jig/dl ("6, 7, 18 rule") [5]. Other authors suggested that a peak cortisol concentration should be greater than or equal to 20 µg/dl [3,6].…”

Glucocorticoid Response to Intramuscular Acth Stimulation in Critically Ill Patients

“…15,16,17 For this reason, in stress, the evaluation of appropriateness of the activation of the HPA axis requires dynamic testing. Adrenal insufficiency is diagnosed when on stimulation test the peak serum cortisol is <500 nmol/L (18 µg/dL), 18 alternatively it has been proposed that increment during ACTH stimulation test <250 nmol/L (9 µg/dL) or basal cortisol <83 nmol/L (3 µg/dL) can be considered as diagnostic of AI. 18,19 Diagnostic evaluation of suspected cases of adrenal insufficiency is hindered by non-availability of injection Synacthen.…”

“…Adrenal insufficiency is diagnosed when on stimulation test the peak serum cortisol is <500 nmol/L (18 µg/dL), 18 alternatively it has been proposed that increment during ACTH stimulation test <250 nmol/L (9 µg/dL) or basal cortisol <83 nmol/L (3 µg/dL) can be considered as diagnostic of AI. 18,19 Diagnostic evaluation of suspected cases of adrenal insufficiency is hindered by non-availability of injection Synacthen. To overcome this limitation, we used Acton Prolongatum (Corticotrophin Carboxymethyl cellulose) as intramuscular ACTH stimulation test.…”