Nelson Syndrome

**Definition:** A syndrome characterized by HYPERPIGMENTATION, enlarging pituitary mass, visual defects secondary to compression of the OPTIC CHIASM, and elevated serum ACTH. It is caused by the expansion of an underlying ACTH-SECRETING PITUITARY ADENOMA that grows in the absence of feedback inhibition by adrenal CORTICOSTEROIDS, usually after ADRENALECTOMY.

**Tree numbers:** - C04.588.322.609.145.500 - C10.228.140.617.738.675.149.500 - C19.344.609.145.500 - C19.700.734.145.500