Evaluation of the association between St. John's wort and elevated thyroid-stimulating hormone.
OBJECTIVE
To evaluate whether St. John's wort is associated with an elevation in thyroid-stimulating hormone (TSH) levels.


METHODS
Retrospective case-control study


METHODS
Hamilton, Ontario; September 1998-May 1999.


METHODS
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.


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).


CONCLUSIONS
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.
Ferko
N
N
Centre for Evaluation of Medicines, Father Sean O'Sullivan Research Centre, and McMaster University, Hamilton, Ontario, Canada.
Levine
M A
MA
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000928:Antidepressive Agents / Q000009:adverse effects*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D020902:Hypericum / Q000009:adverse effects*; D007037:Hypothyroidism / Q000139:chemically induced; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013972:Thyrotropin / Q000097:blood*
D000928:Antidepressive Agents; D013972:Thyrotropin