FAILURE TO RESPOND TO GROWTH HORMONE RELEASING HORMONE (GHRH) IN ACROMEGALY DUE TO A GHRH SECRETING PANCREATIC TUMOR: DYNAMICS OF MULTIPLE ENDOCRINE TESTING

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Abstract
Growth hormone releasing hormone (GHRH) was recently isolated and sequenced from pancreatic tumors secreting GHRH. Patients with untreated acromegaly due to a pituitary tumor respond to exogenous administration of GHRH with a further rise of their elevated basal growth hormone (GH) levels. The effects of exogenously administered synthetic GHRH in a patient with acromegaly due to a GHRH secreting pancreatic tumor are reported. The diagnosis was established by high peripheral IR[immunoreactive]-GHRH levels (1100 pg/ml) and an arterio- venous tumor gradient of IR-GHRH. In this patient GH failed to respond to 1 .mu.g/kg of exogenous GHRH with the pancreatic tumor in situ; further increase of serum GH levels occurred after TRH administration, hypoglycemia and oral glucose administration. After removal of the tumor, serum GH levels decreased and a normal response to GHRH and TRH were demonstrated. The extract of the tumor contained 1.7 .mu.g IR-GHRH/g wet tissue. Thus, lack of response to exogenous GHRH in untreated acromegaly may indicate the presence of an ectopic GHRH producing tumor.