In this interview, Dr. Hennessey describes the history, refinements, implementation, physiology, and clinical outcomes achieved over the past several centuries of thyroid hormone replacement strategies. Topics discussed in this episode include: The history of levothyroxin Chinese using thyroid hormone to treat cretinism in the 6th century What is cretinism? Dangers of hypothyroidism during pregnancy Prescribed 3-step process when hypothyroidism is treated when pregnant The history of sheep thyroid as a treatment? In the 1920's thyroid hormone was synthesized T3 was synthesized in the 1950's When to take thyroid medication, morning or night? A rich history of physician intervention in thyroid dysfunction was identified dating back more than 2 millennia. Although not precisely documented, thyroid ingestion from animal sources had been used for centuries but was finally scientifically described and documented in Europe over 130 years ago. Since the reports by Bettencourt and Murray, there has been a continuous documentation of outcomes, refinement of hormone preparation production, and updating of recommendations for the most effective and safe use of these hormones for relieving the symptoms of hypothyroidism. As the thyroid extract preparations contain both levothyroxine (LT4) and liothyronine (LT3), current guidelines do not endorse their use as controlled studies do not clearly document enhanced objective outcomes compared with LT4 monotherapy. Among current issues cited, the optimum ratio of LT4 to LT3 has yet to be determined, and the U.S. Food and Drug Administration (FDA) does not appear to be monitoring the thyroid hormone ratios or content in extract preparations on the market. Taken together, these limitations are important detriments to the use of thyroid extract products. James V. Hennessey, MD is Director of Clinical Endocrinology at Beth Israel Deaconess Medical Center in Boston, MA. He is an Associate Professor of Medicine at the Harvard medical School. He completed medical training at the Medical Faculty of the Karl Franzens University in Graz Austria. He served as an Intern and Medical Resident at the New Britain Hospital in Connecticut. He entered active duty with the USAF Medical Corps as an Internist/Flight Surgeon after residency and later completed subspecialty training in endocrinology and metabolism at the Walter Reed Army Medical Center in Washington DC where he conducted research in thyroxine bioequivalence. Following fellowship Dr. Hennessey served as the Chief of Endocrinology at USAF Medical Center Wright-Patterson in Ohio and later joined the faculty at Wright State University School of Medicine as the Director of Clinical Clerkships. Top 10 most prescribes drugs in the U.S. (monthly) - Monthly prescriptions, nearly 22 million