Absorption of levothyroxine
Approximately 62-82% of levothyroxine is absorbed after oral administration.Early reports described elevated serum TSH levels in patients with coeliac sprue and inflammatory bowel disease despite thyroxine doses that had previously normalised serum levels.Patients with jejunoileal bypass surgery or other bowel resection have been reported to require higher doses of levothyroxine following surgery.2, 3, 4 Stone et al. noted reduced peak
Food and dietary fibre
Absorption of levothyroxine has been shown to be influenced both by the timing of food intake and by certain foods.Using the double-isotope method developed by Hays, the authors showed that absorption was significantly better in the fasting state
Gastrointestinal disorders
Both malabsorptive disorders and conditions that impair gastric acidity can affect the bioavailability of levothyroxine.