What type of testing is negative in patients with Addison's disease?

In Addison's disease, the adrenal glands are underactive and do not produce sufficient amounts of cortisol. When evaluating patients suspected of having this condition, an ACTH stimulation test is typically conducted. In a healthy individual, administration of ACTH should prompt the adrenal glands to produce cortisol. However, in Addison's disease, the adrenal glands are unable to respond adequately to ACTH, resulting in low cortisol levels despite elevated ACTH. This inability to produce cortisol in response to stimulation is what makes the ACTH testing a negative indicator for Addison's disease.

The other testing options listed include cortisol testing, which is directly affected in Addison's disease and would typically show low cortisol levels; thyroid function testing, which is unrelated to Addison's disease; and electrolyte testing, where one would often see an imbalance, such as hyperkalemia and hyponatremia, due to adrenal insufficiency. Together, these assessments help provide a clearer understanding of Addison's disease and its impact on hormone production and electrolyte balance.