When a patient suffering from acromegaly is found to have a pancreatic endocrine tumour and the latter does not show any humoral syndrome, then two possibilities will be considered: one is that the patient has MEN type I, possessing both a pituitary tumour and an asymptomatic pancreatic endocrine tumour; the other is that the patient's pancreatic endocrine tumour produces GHRH, which in turn stimulates growth hormone secretion from the pituitary, resulting in acromegaly. In the latter case, the plasma GHRH level is one hundred- to one thousand-fold higher than the normal value (upper limit of normal is approximately l00pg/ml) and is useful for the differential diagnosis.
