Endocrine Abstracts

Overt primary adrenocortical failure is preceded by several stages of subclinical hypoadrenocorticolism. Individuals with type 1 diabetes (T1D) or who have other autoimmune conditions are at risk for the development of Autoimmune Addison's disease (AAD). These at risk individuals can be identified by the detection of adrenal autoantibodies (AAb).

The aim of this study was two fold: firstly, to evaluate the sensitivity of early morning cortisol: ACTH ratio in 68 subjects, as an early indication to repeat a short synacthen test (SST) for AAb positive individuals. Secondly, a retrospective analysis of all AAb (detected using an immunoflourescence method) positive subjects during the last 5 years were analysed. The outcome of AAb positive individuals without the initial evidence of hypocortisolaemia was followed up for their progression.

Twenty-two subjects were positive for AAb. Eight subjects were diagnosed with AAD at onset of testing for AAb. The remaining 14 subjects with AAb were deemed not having AAD due to them passing a SST. Four out of these 14 subjects developed AAD after a mean follow up of 3.7 years. An early morning cortisol: ACTH ratio < 6 had a sensitivity and specificity of 100% in diagnosing AAD (failure on a SST) in 68 subjects. All four subjects that developed AAD had an early morning cortisol: ACTH ratio < 6 and had a pre- existing autoimmune condition.

There have been no clear guidelines or consensus on monitoring subjects with AAb. We demonstrate that co-existing autoimmune diseases and a low cortisol:ACTH ratio will guide clinicians to further investigate these subjects with a SST. Further assessment with renin/aldosterone, HLA status and newer radioimmunoassays detecting 21 hydroxylase autoantibodies may also add to the prediction of primary adrenocorticol failure