8
Conditions and drugs interfering with thyroxine absorption

https://doi.org/10.1016/j.beem.2009.06.006Get rights and content

Food, dietary fibre and espresso coffee interfere with the absorption of levothyroxine. Malabsorptive disorders reported to affect the absorption of levothyroxine include coeliac disease, inflammatory bowel disease, lactose intolerance as well as Helicobacter pylori (H. pylori) infection and atrophic gastritis. Many commonly used drugs, such as bile acid sequestrants, ferrous sulphate, sucralfate, calcium carbonate, aluminium-containing antacids, phosphate binders, raloxifene and proton-pump inhibitors, have also been shown to interfere with the absorption of levothyroxine.

Section snippets

Absorption of levothyroxine

Approximately 62–82% of levothyroxine is absorbed after oral administration. This absorption occurs within the first 3 h of ingestion and is localised mainly in the jejunum and ileum.1 The absorption of levothyroxine is maximal when the stomach is empty, reflecting the importance of gastric acidity in this process. 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. This was first reported by Wenzel et al. in their study comprising 37 patients.13 Subjects ingested either 100 μg or 3 mg of levothyroxine under two settings: (1) fasting, or (2) immediately before the consumption of two buttered rolls and a boiled egg. 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. 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. These findings suggest that pre-existing malabsorption can reduce the bioavailability of levothyroxine. This association appears to be strongest with coeliac disease. More recently, a study has

Medications

Several commonly used oral medications have been shown to alter the bioavailability of levothyroxine, many of which interfere by forming an insoluble or non-absorbable complex with levothyroxine.

Conclusion

Various endogenous and exogenous factors can change the absorption kinetics of levothyroxine. The timing of food intake in relation to levothyroxine administration is important, and it is recommended to delay food by at least 60 min following ingestion. Fibre and espresso coffee have been shown to interfere, indicating that the content of dietary intake is also important. Disorders of malabsorption or impaired gastric acidity can reduce the absorption of levothyroxine, and resistant

Conflict of interest

The authors have no conflicts of interest to declare.

References (45)

  • M. Vanderschueren-Lodeweyckx et al.

    Decreased serum thyroid hormone levels and increased TSH response to TRH in infants with celiac disease

    Clinical Endocrinology (Oxford)

    (1977)
  • G. Csako et al.

    Exaggerated levothyroxine malabsorption due to calcium carbonate supplementation in gastrointestinal disorders

    Annals of Pharmacotherapy

    (2001)
  • M.T. Hays

    Absorption of oral thyroxine in man

    The Journal of Clinical Endocrinology and Metabolism

    (1968)
  • D.G. Read et al.

    Absorption of oral thyroxine in hypothyroid and normal man

    The Journal of Clinical Endocrinology and Metabolism

    (1970)
  • K. Hasselström et al.

    The bioavailability thyroxine and 3,5,3′-triiodothyronine in normal subjects and in hyper- and hypothyroid patients

    Acta Endocrinologica (Copenh)

    (1985)
  • M.A. Greenstadt et al.

    Non-isotopic method for determination of oral thyroxine absorption

  • J.T. Nicoloff et al.

    Simultaneous measurement of thyroxine and triiodothyronine peripheral turnover kinetics in man

    The Journal of Clinical Investigation

    (1972)
  • Y. Liel et al.

    Evidence for a clinically important adverse effect of fiber-enriched diet on the bioavailability of levothyroxine in adult hypothyroid patients

    The Journal of Clinical Endocrinology and Metabolism

    (1996)
  • A.C. Chiu et al.

    Effects of pharmacological fiber supplements on levothyroxine absorption

    Thyroid

    (1998)
  • S. Benvenga et al.

    Altered intestinal absorption of L-thyroxine caused by coffee

    Thyroid

    (2008)
  • L. D'Estève-Bonetti et al.

    Gluten-induced enteropathy (coeliac disease) revealed by resistance to treatment with levothyroxine and alfacalcidol in a sixty-eight-year-old patient: a case report

    Thyroid

    (2002)
  • C.M. Silva et al.

    Autoimmune hypothyroidism nonresponsive to high doses of levothyroxine and severe hypocalcemia

    Arquivos Brasileiros de Endocrinologia e Metabologia

    (2005)
  • Cited by (171)

    • Ultrasonic investigation of molecular interaction of thyroxine and anti-tuberculosis drugs and DFT studies

      2021, Journal of the Indian Chemical Society
      Citation Excerpt :

      A recent study assessed levothyroxine dosage along with drugs like sucralfate, cholestyramine and proton pump inhibitors and found that these drugs can impair levothyroxine absorption. These studies also proved that these drugs can affect levothyroxine metabolism [11–15]. The assessment of strength of molecular interaction of drug with enzymes and hormones and also understanding the mechanism of drug action will be helpful in drug design [16].

    • Levothyroxine dose adjustment in hypothyroid patients following gastric sleeve surgery

      2020, Annales d'Endocrinologie
      Citation Excerpt :

      As not all patients received these treatments, and those that did were given different dosages and varying lengths of treatment, variations in absorption could well arise causing knock-on effects on levothyroxine dose. Certain digestive disorders can alter levothyroxine absorption: coeliac disease, gastritis, lactose intolerance and digestive tract inflammatory disease (Crohn) [28,31]. We do not have a record of such digestive pathologies in our study.

    View all citing articles on Scopus
    View full text