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 Gushing's syndrome and Ac romegaly. At the age of 28 she was diagnosed with Gushing's syndrome due to a left adrenal tumor concomitant with a GH-producing pituitary tumor. Befo re 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 adrenocortic al adenoma was removed by adrenalectomy. During the four months after the a drenalectomy, basal GH levels dramatically decreased and the high-density m ass 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 reappear ance of the pituitary tumor. In order to examine the glucocorticoid depende ncy on GH secretion, we compared the GH secretion in a series of endocrinol ogical tests before and after oral 8 mg dexamethasone administration for 7 days. There was no difference between before and after dexamethasone admini stration in the GH secreting pattern, but basal GH levels were apparently i ncreased after dexamethasone treatment. Transsphenoidal surgery was done an d pathological examination showed a GH-producing pituitary adenoma. In vitr o, dexamethasone increased GH secretion from the cultured GH-producing aden oma cells in a-dose-dependent manner. In this case, both GH secretion and p ituitary tumor growth seemed to be dependent on glucocorticoid.