Hyperhomocysteinemia in Hypothyroidism

  1. Charles Faiman, MD;
  2. Donald W. Jacobsen, PhD; and
  3. Ralph Green, MD
  1. The Cleveland Clinic Foundation; Cleveland, OH 44195 (Faiman) The Cleveland Clinic Foundation; Cleveland, OH 44195 (Jacobsen) University of California; Sacramento, CA 95817 (Green)

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    IN RESPONSE:

    We thank Dr. Weiss for underscoring a potential renal mechanism by which L-thyroxine normalizes the hyperhomocysteinemia seen in hypothyroidism. To examine the relation between homocysteine and GFR, we retrospectively examined serum creatinine levels (as a surrogate for GFR) in 13 of the 14 patients for whom frozen specimens were still available from our study.

    We confirm the findings of Kreisman and Hennessey (1) indicating a decline in serum creatinine levels in hypothyroid persons after the attainment of euthyroidism with L-thyroxine replacement. The median serum creatinine values decreased significantly from the hypothyroid to the euthyroid state—from 1.0 mg/dL (range, 0.8 to 1.8 mg/dL) to 0.8 mg/dL (range, 0.6 to 1.1 mg/dL), a difference of 0.2 mg/dL (range, 0.0 to 0.7 mg/dL), or 23.1% (range, 0% to 39%) (sign test, P < 0.001). The positive association between plasma homocysteine and serum creatinine levels in the hypothyroid state (Spearman rank correlation r = 0.69; P = 0.009) adds further credence to a cause-and-effect linkage between elevated homocysteine levels and reduced GFR, whereas the lack of a relation between the decline in homocysteine and creatinine levels after therapy (r = 0.39; P = 0.19) does not. We conclude that the exact mechanisms by which L-thyroxine normalizes the elevated circulating homocysteine levels in hypothyroidism requires further study. Regardless, the major finding of our reported study still stands: namely, that L-thyroxine replacement therapy corrects the hyperhomocysteinemia of hypothyroidism.

    Charles Faiman, MD

    The Cleveland Clinic Foundation; Cleveland, OH 44195

    Donald W. Jacobsen, PhD

    The Cleveland Clinic Foundation; Cleveland, OH 44195

    Ralph Green, MD

    University of California; Sacramento, CA 95817

    The Editors welcome submissions for possible publication in the Letters section. Authors of letters should:

    •Include no more than 300 words of text, three authors, and five references

    •Type with double-spacing

    •Send three copies of the letter, an authors' form signed by all authors, and a cover letter describing any conflicts of interest related to the contents of the letter.

    Letters commenting on an Annals article will be considered if they are received within 6 weeks of the time the article was published. Only some of the letters received can be published. Published letters are edited and may be shortened; tables and figures are included only selectively. Authors will be notified that the letter has been received. If the letter is selected for publication, the author will be notified about 3 weeks before the publication date. Unpublished letters cannot be returned.

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    Reference

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