Serum TSH and the influence of statin drugs.

Objectives To investigate a possible, previously unreported association between statin drugs and a low serum TSH

Methods 307 consecutive patients referred to the Nuclear Medicine Service for presumed hyperthyroidism on the basis of a low serum TSH were reviewed. The clinical evaluation and the radioiodine uptakes and scans were utilized to form a final diagnosis.

Results 278 patients (84%) not taking statins had elevated uptakes and were diagnosed hyperthyroid, while only 13 of 29 patients (16%) of the statin patients had high uptakes. 16 patients were diagnosed euthyroid (p<0.001). The age- and sex-adjusted odds ratio of a statin user with a low serum TSH having normal RAI was 3.6 (95% CI, 1.6-8.4).

Conclusions Statin drugs may falsely lower the serum TSH without altering thyroid function. The cause of this phenomenon is not known.