Thyroxine malabsorption following intestinal bypass surgery.

Jejuno-ileal bypass surgery for morbid obesity results in small bowel malabsorption. This may produce various nutritional or mineral deficiencies. A patient who became hypothyroid following bypass surgery required a larger than normal dose of thyroxine, presumably because of impaired absorption. In such patients it is particularly important to measure serum thyrotrophin concentrations in assessing the replacement dose of thyroxine.