Prospective studies of thyroid function in patients receiving gold therapy.

ABSTRACT

Gold inhibits the Type I deiodinase that provides the bulk of circulating T3 in humans. We prospectively studied thyroid function in patients receiving increasing parenteral cumulative gold doses. Eight consecutive euthyroid patients with rheumatoid or psoriatic arthritis who were initiating intramuscular gold therapy were enrolled. Serum thyroid hormone levels (total T4, T3, and rT3) and TSH were measured for each subject at various levels during gold therapy. For analysis, the free T4 and free T3 indices, TSH concentrations, and T4/T3 ratios were correlated with cumulative gold dose. Neither individual nor pooled linear regressions showed a significant correlation between cumulative gold dose and any of the thyroid function parameters. Thyroid function is not affected in patients receiving up to 1500 mg of gold compounds. The most likely explanation for this is that gold principally accumulates in the Kupffer cells and renal cortex and these cells do not express Type I deiodinase.