Evaluation of the Association Between St. John's Wort and Elevated Thyroid‐Stimulating Hormone Journal Articles uri icon

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abstract

  • Study Objective. To evaluate whether St. John's wort is associated with an elevation in thyroid‐stimulating hormone (TSH) levels.Design. Retrospective case‐control study.Setting. Hamilton, Ontario; September 1998–May 1999.Subjects. Thirty‐seven subjects with elevated TSH levels and 37 age‐ (± 6 yrs) and gender‐matched subjects with normal TSH levels who resided in the same region.Measurements and Main Results. Exposure to St. John's wort during the 3–6 months before TSH measurement was assessed through a telephone interview. A total of 4 of 37 subjects with elevated TSH levels and 2 of 37 subjects with normal TSH levels had taken St. John's wort in that time period. The odds ratio for elevated TSH levels associated with taking St. John's wort was 2.12 (95% confidence interval [CI] 0.36–12.36).Conclusion. This study suggests a probable association between St. John's wort and elevated TSH levels. However, because of the wide CIs surrounding the point estimate (which crosses unity), further investigation, including a large, prospective cohort study, is warranted.

publication date

  • December 2001