What is the most common cause of secondary adrenal insufficiency?

Prolonged steroid use is recognized as the most common cause of secondary adrenal insufficiency due to the impact it has on the hypothalamic-pituitary-adrenal (HPA) axis. When exogenous glucocorticoids are administered over an extended period, they can suppress the production of adrenocorticotropic hormone (ACTH) from the pituitary gland. This suppression occurs because the body perceives sufficient levels of circulating cortisol and thus reduces the stimulation of the adrenal glands. As a result, the adrenal glands may atrophy, leading to insufficient cortisol production when the steroid therapy is stopped or reduced, manifesting as adrenal insufficiency.

Understanding the other options offers clarity on the context. Autoimmune disorders, such as Addison's disease, are more commonly associated with primary adrenal insufficiency rather than secondary. Infections can lead to adrenal crises but are less frequent as a cause of chronic secondary adrenal insufficiency. Trauma might lead to adrenal hemorrhage or direct damage to the adrenal glands, impacting their function, but it is not a prevalent cause of secondary adrenal insufficiency compared to the effects of prolonged steroid use.