What effect does a cosyntropin stimulation test have on cortisol levels in primary adrenal insufficiency?

In primary adrenal insufficiency, the adrenal glands are not able to produce adequate amounts of cortisol due to damage to the adrenal cortex. The cosyntropin stimulation test evaluates adrenal function by administering a synthetic form of adrenocorticotropic hormone (ACTH), which normally stimulates the adrenal glands to produce cortisol.

In individuals with primary adrenal insufficiency, the damaged adrenal glands are incapable of responding effectively to the administration of cosyntropin. As a result, there will be no significant increase in cortisol levels following the stimulation test. This lack of response confirms the diagnosis of primary adrenal insufficiency, as healthy adrenal glands would show a significant increase in cortisol levels when stimulated with ACTH.

This understanding is crucial in differentiating between types of adrenal dysfunction and guiding appropriate management of conditions like Addison's disease.