From: Lawrence C. Wood, MD [lcw1@comcast.net]
Sent: Wednesday, November 26, 2003 7:38 AM
To: fdadockets@oc.fda.gov
Subject: 2003P-0387 re thyroxine bioequivalence

To the FDA:
I am writing as CEO and Medical Director of the Thyroid Foundation of America to urge you to consider a broader approach to thyroxine bioequivalence.

We are concerned that the FDA is not considering the TSH test as the most sensitive way to evaluate bioequivalence of thyroxine products, for we know that even a small change in dose (eg 12.5 mcg) can change the TSH level.  To much thyroxine can make a person subclinically hyperthyroid with no symptoms and yet (especially in older individuals) an increased risk for atrial fibrillation and heart attacks.  To little hormone could have major adverse effects for cancer patients that must have thyroid supression to prevent cancer recurrences.

Even changing brands can result in a change it TSH with the above consequences, even though the strength of the tablets is supposed to be the same.  We advise our members and the thousands of individuals that contact our website and our office not to change brands of thyroxine. 

We feel that the FDA should consider these factors and we join the ATA, Endocrine Society, and AACE to recommend that the FDA organize a workshop to consider its bioequivalence standards.

Sincerely yours,
Lawrence C. Wood, MD
CEO and Medical Director, Thyroid Foundation of America