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Normal T4 Ranges in Pregnancy

Last Updated: · Doctors
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Question

All along,I thought that free hormone levels (ft4/ft3) are better initialparameters (vs t4) in monitoring treatment in pregnant patients with toxic goiter. In the march 2006 issue of Endocrinology and met clinics of NA, the authors, recommend measuring total t4 concentration for dose titration of anti thyroid drug. Can you comment on this. Thanks again.

Lynn F. W. Bilar, MD

Response

There is no perfect answer to your question. If laboratory trimester-specific “normal pregnancy” values are available, then freeT4 values using this range would be fine. However these are not generally available. An approachthat seems generally safe is to adjust therapy using total T4 values,assuming that the normal pregnancy range is 1.5 times the non-pregnant range. Some guidelines on this topic will soon be published by the Endocrine Society.

L De Groot, MD