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348        SEcTion iii    EndocrinE  ` endocrine—PAthology                                                                                                                  EndocrinE  ` endocrine—PAthology





               Cushing syndrome
                etiology              cortisol due to a variety of causes:
                                         ƒ Exogenous corticosteroids Ž  ACTH Ž bilateral adrenal atrophy. Most common cause.
                                         ƒ Primary adrenal adenoma, hyperplasia, or carcinoma Ž  ACTH Ž atrophy of uninvolved
                                        adrenal gland.
                                         ƒ ACTH-secreting pituitary adenoma (Cushing disease); paraneoplastic ACTH secretion (eg,
                                        small cell lung cancer, bronchial carcinoids)Ž bilateral adrenal hyperplasia. Cushing disease is
                                        responsible for the majority of endogenous cases of Cushing syndrome.
                Findings             CUSHING Syndrome:  Cholesterol,  Urinary free cortisol, Skin changes (thinning, striae  A ),
                                       Hypertension, Immunosuppression, Neoplasm (a cause, not a finding), Growth retardation (in
                                       children),  Sugar (hyperglycemia, insulin resistance). Also, amenorrhea, moon facies  B , buffalo
                                       hump, osteoporosis,  weight (truncal obesity), hirsutism.
                diAgnosis            Screening tests include:  free cortisol on 24-hr urinalysis,  late night salivary cortisol, and no
                                      suppression with overnight low-dose dexamethasone test.

               A                                      ↑ 24-hr urine free cortisol, ↑ late night salivary cortisol, and/or
                                                      inadequate suppression on 1 mg overnight dexamethasone test


                                                             Measure serum ACTH

                                          Suppressed                                 Elevated


               B                        ACTH-independent                          ACTH-dependent
                                        Cushing syndrome                          Cushing syndrome


                                      Exogenous glucocorticoids
                                         or adrenal tumor         High-dose dexamethasone        CRH stimulation test
                                                                     suppression test
                                     (consider adrenal CT to confirm)

                                                                                                           ↑
                                                                                                         No      in ACTH
                                                              No suppression  Adequate                      and cortisol
                                                              Ectopic ACTH   suppression  ↑ ACTH and cortisol
                                                               secretion    Cushing disease  Cushing disease  Ectopic ACTH
                                                                                                           secretion
                                                         CT of the chest/abdomen/pelvis  MRI of the pituitary  CT of the chest/abdomen/pelvis






               Nelson syndrome       Enlargement of pre-existing ACTH–secreting pituitary adenoma after bilateral adrenalectomy for
                                      refractory Cushing disease Ž  ACTH (hyperpigmentation), mass effect (headaches, bitemporal
                                      hemianopia).
                                     Treatment: transsphenoidal resection, postoperative pituitary irradiation for residual tumor.





















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