Neurohormonal factors in functional dyspepsia: insights on pathophysiological mechanisms. Neurohormonal factors were investigated in 10 patients with functional dyspepsia who had normal or slow upper gut transit and 10 age- and sex-matched healthy controls. Gastric and small bowel motility and transit, jejunal responses to luminal distention and IM neostigmine, gut hormones, and vagal and sympathetic functions were studied. Slow upper gut transit was defined by a gastric emptying slope less than 0.3%/min or 10% small bowel transit time greater than 300 minutes. Four patients with slow transit had reduced postprandial antral motility and gut hormone responses. Two of the four patients had vagal and sympathetic dysfunction. In 6 patients with normal transit, balloon distention in the jejunum was perceived at a lower volume (32.7 +/- 5.9 mL) than in controls (46.6 +/- 3.0 mL). Pressure responses to balloon distention were reduced in 5 and exaggerated in 1 patient; abnormal efferent vagal (2 patients) and sympathetic (1 patient) function were also documented. In view of the normal transit, motility, and jejunal pressure responses to neostigmine in all 6 patients, the abnormal response to distention suggests afferent dysfunction. Functional dyspepsia is a heterogenous disorder. Abnormal transit is sometimes associated with disorders of extrinsic neural control, but the latter are also found in patients with normal transit. Increased perception of intraluminal stimuli in those with normal transit suggests a disturbance in afferent function. 