A family with multiple endocrine neoplasia type I (MEN-I) is described in which three members had A-cell pancreatic tumors. Two of these members had classic glucagonoma syndromes. The proband, a 62 ...year old woman, had a high (less than or equal to 9.2 ng/ml) basal plasma glucagon level, most of which eluted in the 3,500 dalton fraction. Plasma glucagon increased following the ingestion of mixed meals and arginine. Secretin, which, in the dog, has been reported to inhibit normal glucagon secretion, provoked a twofold increase in 3,500 dalton plasma glucagon concentration. Increased plasma glucagon in the proband was associated with mild hyperglycemia and insulin resistance. Somatostatin infusion suppressed peripheral glucagon and insulin levels, and increased blood glucose levels. The unique responses to secretin and somatostatin observed in this patient may be diagnostically important in syndromes of inappropriate or autonomous glucagon secretion.
