A 22-year-old woman presents with chronic diarrhea. She has no abdominal discomfort, feels well, and reports no weight loss or systemic symptoms. Physical examination reveals a healthy young woman who is 5'7" tall and weighs 170 lb. The complete physical examination is normal. Which of the following is the most likely cause of a secretory diarrhea in this young woman?

In this young woman, after considering other causes, surreptitious use of laxatives needs to be considered. Abuse of stimulant laxatives such as senna can cause a secretory diarrhea. Magnesium-based laxatives will cause an osmotic diarrhea. Although carcinoid tumor can cause diarrhea, it is an uncommon disorder and she should have other symptoms of carcinoid such as flushing or skin changes. Celiac disease and UC can cause diarrhea but would have associated weight loss or abdominal discomfort. Lactose deficiency does not cause a secretory diarrhea but an osmotic diarrhea.