Secondary Hyperadrenalism: Cushing's Disease

Secondary hyperadrenalism is often referred to as Cushing's disease because the pathology lies specifically within the pituitary gland and excess ACTH production. Cushing's syndrome is used as a more general term associated with any pathology that causes excess cortisol.

Secondary hyperadrenalism can be caused by certain infections, cancer, trauma, or idiopathically. The signs and symptoms of secondary hyperadrenalism are similar to primary adrenalism because there is still extra cortisol being produced. Signs and symptoms include upper body obesity, rounded face, increased neck and shoulder fat (buffalo hump), thin arms and legs, fragile skin, stretch marks on various body sites, muscle and bone weakness, hypertension, hyperglycemia, irritability/anxiety, excess facial hair in women, irregular menstrual cycles, and reduced fertility in men.

Dexamethasone suppression testing is used for diagnosing Cushing's disease. Dexamethasone works by resembling cortisol to inhibit the production of ACTH from the pituitary gland, decreasing cortisol levels. It can be given in high and low doses. In the morning, if cortisol is still high and ACTH is high in both the low and high doses, then it can be determined that an ectopic tumor is present producing ACTH because the pituitary should be inhibited from producing ACTH. This is useful for determining secondary hyperadrenalism from ectopic causes of hyperadrenalism.