Endocrine Abstracts

A young female presented concerned that she may have Addison’s disease. She had noted increasing pigmentation and reported her sister had died from undiagnosed Addison’s disease. She was hypotensive, with no postural drop in her blood pressure. She was hyponatraemic and hyperkalaemic. An initial 250 μg Synacthen test performed in the afternoon gave a baseline cortisol of 258 nmol/L and a 30 minute cortisol of 291 nmol/L. In view of this, the Synacthen test was repeated and once again she had a reasonable baseline cortisol but a sub-optimal response (291 nmol/L increasing to 326 nmol/L). Adrenal cortex antibodies were found to be positive.

It is now recognised that Addison’s disease may have a long pre-clinical phase. In addition to patients with existing autoimmune disease, patients with a family history are at increased risk of developing Addison’s disease. These patients are often antibody positive for some time prior to the development of pre-clinical Addison’s disease and differentiating these patients with potential Addison’s disease from those with pre-clinical disease can be problematic. Pre-clinical Addison’s disease is defined as the presence of autoantibodies, with a normal baseline cortisol, an inadequate response to Synacthen and the absence of clinical features. However, our patient despite having the first 3 of these was symptomatic.

This patient reminds us that a ‘normal’ random cortisol in the presence of positive adrenal autoantibodies, does not rule out Addison’s disease and that a 250 μg Synacthen test is required to adequately assess adrenal reserve. Our patient failed her 250 μg Synacthen test, however, if we had seen her earlier in the disease process this may not have been the case, and there is a suggestion that a 1 μg Synacthen test may be useful in this situation.