A case of somatostatinoma: responses to food and SMS 201-995 administration

Plasma somatostatin response to food and the administration of the long-acting somatostatin analogue SMS 201-995, as well as pituitary responses to insulin-induced hypoglycemia, growth hormone-releasing hormone (GHRH) and thyrotropin-releasing hormone (TRH), were assessed in a 60-year-old woman with biopsy-proven metastatic somatostatinoma. SMS 201-995 alone did not change plasma somatostatin-like immunoreactivity (SRIF), but levels of low-molecular-weight forms (SRIF-14 and SRIF-28) more than doubled in response to a standard meal. This postprandial response was not affected by pretreatment with SMS 201-995. Although a growth hormone response to insulin-induced hypoglycemia and supramaximal GHRH was absent, the patient's thyroid-stimulating hormone response to TRH was normal. These results suggest that somatostatin analogues may not influence tumor autonomy and that a SRIF response to food may contribute to early satiety in patients with somatostatinoma. In addition, the long-term use of somatostatin analogues to suppress hormone production by other peptide-secreting tumors may not have predictable results.