Thyroxine in goiter, H. pylori infection, and gastritis

Levothyroxine Interactions with Food and Dietary Supplements-A Systematic Review

Levothyroxine (l-thyroxine, l-T4) is a drug of choice for treating congenital and primary hypothyroidism. Although clinically significant interactions between l-T4 and food can alter the safety and efficacy of the treatment, they still seem to be generally underestimated by patients, physicians and pharmacists. This review aimed to investigate the effects of meals, beverages, and dietary supplements consumption on l-T4 pharmacokinetics and pharmacodynamics, to identify the most evident interactions, and to perform the recommendations for safe co-administering of l-T4 and food. A total of 121 studies were identified following a systematic literature search adhering to PRISMA guidelines. After full-text evaluation, 63 studies were included. The results proved that l-T4 ingestion in the morning and at bedtime are equally effective, and also that the co-administration of l-T4 with food depends on the drug formulation. We found limited evidence for l-T4 interactions with coffee, soy products, fiber, calcium or iron supplements, and enteral nutrition but interestingly they all resulted in decreased l-T4 absorption. The altered l-T4 efficacy when ingested with milk, juices, papaya, aluminium-containing preparations, and chromium supplements, as well as observed enhancement effect of vitamin C on l-T4 absorption, shall be further investigated in larger, well-designed studies. Novel formulations are likely to solve the problem of coffee, calcium and iron induced malabsorption of l-T4. Maintaining a proper time interval between l-T4 and food intake, especially for coffee and calcium, or iron supplements, provides another effective method of eliminating such interactions.

The role of Helicobacter pylori in patients with hypothyroidism in whom could not be achieved normal thyrotropin levels despite treatment with high doses of thyroxine

BACKGROUND

 Helicobacter pylori infection is a most frequent cause of chronic gastritis. H. pylori may decrease absorption of oral thyroxine by decreasing gastric acid secretion in the stomach. In this study, we aimed to investigate the change in thyroid function tests of the cases after H. pylori eradication who were not responding to high doses of thyroxine treatment before H. pylori eradication.

METHODS

 Hypothyroid cases who were not responding to high doses of thyroxine among the ones presented to Endocrinology and Gastroenterohepatology Clinics of Sisli Etfal Training and Research Hospital between 2009 and 2010 were included in the study. Thyroid function tests were performed two times in all cases before and after H. pylori eradication. Duodenal, antral and corporal biopsies, and jejunal aspirates and biopsies were taken during upper gastrointestinal system endoscopies performed in all patients. Cases without intestinal pathology were included in the study.

RESULTS

Serum thyrotropin (TSH), free T3, and free T4 values before H. pylori eradication were 30.5 ± 28.8 IU/mL, 2.64 ± 0.56 pg/mL, and 0.92 ± 0.32 ng/mL, respectively, and after eradication were found to be 4.2 ± 10.6 IU/mL, 3.02 ± 0.61 pg/mL, and 1.3 ± 0.34 ng/mL, respectively (p values <.001, .002, and <.001, respectively). After H. pylori eradication treatment, TSH decreased in all of the cases, factitious thyrotoxicosis developed in % 21 of these cases.

CONCLUSION

In hypothyroid cases, H. pylori gastritis may be responsible for an inadequate response to the treatment. H. pylori eradication in the cases receiving high doses of thyroxine has a risk for thyrotoxicosis.