A 49-year-old man with diarrhea has fluid loss. What therapy can counteract the effects of vasoactive intestinal peptide?

• A. Somatostatin
• B. Aldosterone
• C. Glucagon
• D. Insulin

Answer: (A)

The correct option is somatostatin, which counteracts the effects of vasoactive intestinal peptide (VIP). VIP is a neuropeptide that plays a significant role in increasing intestinal water and electrolyte secretion. In conditions characterized by excessive VIP (such as VIPoma), this can lead to severe diarrhea and fluid loss, manifesting clinically as watery diarrhea.

Somatostatin functions as an inhibitory hormone that counteracts various gastrointestinal hormones, including VIP. By inhibiting the release of VIP and other gastrointestinal secretions, somatostatin decreases fluid and electrolyte loss in the intestine, thereby helping to manage diarrhea and restore fluid balance.

While the other options play roles in metabolic processes or fluid regulation, they do not specifically target the vasoactive effects of VIP in the same manner that somatostatin does. Aldosterone primarily regulates sodium reabsorption and potassium secretion in the kidneys, glucagon primarily influences blood glucose levels, and insulin mainly facilitates glucose uptake in tissues. None of these actions would directly counteract the effects of VIP and rectify the fluid loss associated with its activity. Thus, somatostatin is the most appropriate therapy for this scenario.