Glucocorticoid-dependency on GH secretion and tumor growth in a GH-producing pituitary adenoma with Cushing's syndrome

We report a rare case of a 40-year-old woman with Cushing's syndrome and Acromegaly. At the age of 28 she was diagnosed with Cushing's syndrome due to a left adrenal tumor concomitant with a GH-producing pituitary tumor. Before adrenal surgery her basal GH levels were extremely high and CT scanning revealed a high-density mass in the sella turcica. A 28 g left adrenocortical adenoma was removed by adrenalectomy. During the four months after the adrenalectomy, basal GH levels dramatically decreased and the high-density mass detected by CT scanning had disappeared but the basal GH levels and IGF-1 had not been normalized. She gradually became acromegalic in the twelve years after the adrenalectomy. At the age of 40 CT scanning showed reappearance of the pituitary tumor. In order to examine the glucocorticoid dependency on GH secretion, we compared the GH secretion in a series of endocrinological tests before and after oral 8 mg dexamethasone administration for 7 days. There was no difference between before and after dexamethasone administration in the GH secreting pattern, but basal GH levels were apparently increased after dexamethasone treatment. Transsphenoidal surgery was done and pathological examination showed a GH-producing pituitary adenoma. In vitro, dexamethasone increased GH secretion from the cultured GH-producing adenoma cells in a dose-dependent manner. In this case, both GH secretion and pituitary tumor growth seemed to be dependent on glucocorticoid.