Background and objective: Addisons disease occurs more frequently in patients with type 1 diabetes mellitus (T1DM) as part of the autoimmune polyendocrine syndromes. There is, however, no such association between adrenal failure and type 2 diabetes mellitus (T2DM). We, therefore, retrospectively audited referrals for short synacthen tests (SST) on patients with T2DM.
Methodology: Seven years retrospective study of indications for and results of SST on patients with T2DM referred for exclusion of adrenal failure. A normal SST was defined as a serum cortisol increase of >200 nmol/l over baseline and peak serum cortisol response >550 nmol/l.
Results: There were 89 referrals SSTs in patients with T2DM. Recurrent hypoglycaemia was the sole indication for a SST in 55 (61.8%) patients and in 4 (4.3%) patients in combination with weight loss (n=1), hyponatraemia (n=1), hypogonadotrophic hypogonadism (n=1) and dizziness without hypotension (n=1). Seventeen (19.0%) SSTs were performed on patients with known or suspected hypothalamicpituitaryadrenal axis disorder including three on long-term steroids. The remaining 12 (13.5%) SSTs were requested because of weight loss (n=3), hyperkalaemia (n=3), hyponatraemia (n=1), postural hypotension (n=3), tiredness (n=1), reduction in insulin requirements (n=1) and to assess adrenal reserve prior to starting thyroxine (n=1). Three (3.2%) patients had suboptimal cortisol responses to synacthen, all of who were on long-term steroid therapy.
Discussion: Addisons disease occurs more frequently only in T1DM and not T2DM. It is recommended that patients with T1DM with unexplained recurrent hypoglycaemia be screened for Addisons disease. This, perhaps, has been inadvertently extrapolated to T2DM since the commonest indication for SST in patients with T2DM was recurrent hypoglycaemia but all had normal SSTs.
Conclusion: Recurrent hypoglycaemia, in the absence of other features of adrenal failure, is not an indication for a short synacthen test in patients with T2DM.