Background: The most common cause of primary adrenal failure (Addison’s disease) in the Western world is autoimmunity characterized by autoantibodies against the steroidogenic enzyme 21-hydroxylase (CYP21, 21OH). Detection of 21OH-autoantibodies is currently used for etiological diagnosis, but how levels of 21OH-antibodies vary over time is not known.
Setting: Samples from the national Norwegian Addison’s Registry and Biobank established in 1996 (N=711). Multi-parameter modelling of the course of 21OH-antibody indices over time.
Results: 21OH antibody positivity is remarkably stable, and >90% of the patients are still positive 30 years after diagnosis. Even though the antibody levels decline with disease duration, it is only rarely that this downturn reaches negativity. 21OH-antibody indices are affected by age at diagnosis, sex, type of Addison’s disease (isolated vs. autoimmune polyendocrine syndrome type I or II) and HLA genotype.
Conclusion: 21OH-autoantibodies are reliable and robust markers for autoimmune Addison’s disease, linked to HLA risk genotype. However, a negative test in patients with long disease duration do not exclude autoimmune etiology.