Neuroendocrine disorders of the gut.

The regulation of gastrointestinal function is known to involve elements of the enteric nervous system. Processes such as secretion, motility, blood flow, and immune function are all influenced by a complex network of neurons whose cell bodies lie in the gut. These neurons use a wide spectrum of substances as neurotransmitters, although the majority use peptides once thought to function only as gut hormones. It has been increasingly recognized that abnormalities of this neuroendocrine regulatory system underlie many gastrointestinal disorders. The most obvious are states of peptide excess found in patients with gut endocrine tumors such as carcinoid, gastrinoma, and somatostatinoma. Conversely, other disorders appear to be related to deficiency states. Examples include both achalasia and Hirschsprung's disease (congenital megacolon), where the loss of inhibitory neural action leads to abnormalities of peristalsis and sphincter function. Evidence for abnormal neuroendocrine regulation leading to disease states is increasing for many other gastrointestinal disorders.