EM1909D "It’s not your thyroid… probably – Controversies in Thyroid Hormone Replacement" (IM GR091319)

Hypothyroidism is one of the most commonly encountered disease states. In the Colorado Heart Study as many as 15% of women over the age of 55 had an abnormal thyroid stimulating hormone (TSH) level. The percentage of people with abnormal thyroid hormone levels continues to increase with age, with the overwhelming majority having low circulating thyroid hormone levels, or hypothyroidism. Currently in the US, approximately 123 million prescriptions for thyroid hormone replacement are dispensed, indicating how prevalent this disease state is.

The only way to adequately treat thyroid hormone deficiency is with thyroid hormone replacement. Controversies exist, however, as to the ideal regimen for such replacement. Historically, the first such supplements were made from pork or bovine thyroid. Desiccated products, particularly of pork derivation are still widely available. Subsequently, synthetic human products of tetrathyiodothyronine (T4) and triiodothyronine (T3) became available. Are synthetic human products superior to pork? Is monotherapy with synthetic T4 just as effective as combination of T3 and T4 or desiccated products as the American Thyroid Association recommends? The purpose of this talk is to explore the available data to answer these questions.

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Target Audience

UT Southwestern faculty, fellows, residents and medical students, community physicians, nurse clinicians, physician assistants and nurses.

Learning Objectives

At the conclusion of this activity, the participant should be able to:

  • Understand the pharmacologic differences in the composition between desiccated pork thyroid products and synthetic thyroid hormone products.
  • Understand that the symptoms of thyroid hormone excess/deficiency are low in specificity. Many patients who are “adequately treated with levothyroxine” still endorse these symptoms. Whether these symptoms reflect inadequate thyroid hormone replacement is controversial.
  • Describe the pathway of thyroid hormone signaling and the controversy that exists in T3-containing thyroid hormone replacement regimens.
Course summary
Available credit: 
  • 1.00 AMA
Course opens: 
Course expires: 

Photo: Alex Tessnow, M.D.Alex Tessnow, M.D., MBA, ECNU
Associate Professor of Internal Medicine
Division of Endocrinology

Dr. Tessnow is a graduate of UT Southwestern Medical School and an Associate Professor of Internal Medicine in the Division of Endocrinology. He specializes in the care of individuals with thyroid disorders, predominantly thyroid nodules and cancer.

Available Credit

  • 1.00 AMA


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