Today at intern report we discussed a case of chronic diarrhea in an elderly woman, found to have Graves' Disease in the absence of the typical signs of hyperthyroidism, short of weight loss. The diagnosis was caught on an all-too-simple TSH test, and Graves was confirmed with antibody testing.
1. Secretory diarrhea tends to be nocturnal, unrelated to food intake, and with a fecal osmotic gap <50.
2. Hyperthyroidism related diarrhea is a type of secretory diarrhea.
3. Older patients with Graves' hyperthyroidism are less likely to have the "classic" symptoms (i.e. heat intolerance, tremor, nervousness, goiter), but a higher prevalence of weight loss, SOB, AFib, and ophthalmopathy. (Some references)
Here is an outline from AAFP on the framework of how to approach chronic diarrhea: