THE OCCURRENCE OF SUBACUTE THYROIDITIS AFTER THE AMELIORATION OF HYPERCORTISOLISM FOLLOWING TRANSSPHENOIDAL SURGERY IN CUSHING'S DISEASE.

Only a few subacute thyroiditis (SAT) cases secondary to hypocortisolemia developed after successfully treating Cushing's disease (CD) have been reported. In this report, we present an SAT case, which developed immediately after discontinuation of steroid treatment for hypocortisolemia after the successful treatment of CD. A 54-year-old female patient who had recently been diagnosed with type 2 diabetes mellitus was admitted to our center with complaints of proximal myopathy and obesity. Serum cortisol did not suppress adequately after the 1 mg dexamethasone suppression test. Pituitary MRI of the patient with increased basal plasma ACTH level revealed a 6 x 5 mm right-sided adenoma. After successful surgical treatment, the patient was given ten months of steroid therapy due to a suppressed corticotroph axis. Shortly after the steroid treatment was discontinued, the patient was admitted with neck pain, fever, and thyrotoxicosis. The patient was diagnosed with SAT, and methylprednisolone treatment was started again. The underlying pathophysiological mechanisms in SAT cases that develop after the treatment of CD can only be speculated. One possible mechanism could be that the glucocorticoid deficiency develops after effective treatment of hypercortisolism alters the immunological responses or generates self-reactive cells and prepares an appropriate environment for the thyrolytic process.