#408 ‒ AMA #89: Thyroid health: interpreting symptoms, diagnosing and treating dysfunction, and navigating the gray zone

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In this "Ask Me Anything" (AMA) episode, Peter takes a deep dive into thyroid health and explains why diagnosing and managing thyroid dysfunction is unusually complex. He begins with the basic biology of the thyroid gland and three commonly measured hormones—free T4, free T3, and TSH. He explains how T4 is converted to the active hormone T3 and the important functions T3 performs throughout the body. He also explains what reverse T3 is and when it may be useful to measure it. Peter then breaks down thyroid blood tests and their limitations and provides a practical framework for evaluating suspected thyroid dysfunction. He explains why symptoms alone are insufficient for diagnosis and reviews the criteria for diagnosing hypothyroidism, along with conditions that can mimic it. He also explores how hypothyroidism can be both underdiagnosed and overtreated and how to navigate subclinical hypothyroidism. Peter discusses treatment with T4 and T3, including why some patients continue to experience symptoms despite standard T4 replacement. He also explains how thyroid medications should be taken to optimize absorption. Additional topics include Hashimoto's disease, thyroid considerations during pregnancy, hyperthyroidism, the risks of excess iodine, and supplements marketed to support thyroid function. Finally, Peter offers guidance for patients who continue to feel unwell despite apparently normal thyroid tests.

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We discuss:

• Why thyroid management is unusually complex and what the thyroid does [2:00];
• Why symptoms are insufficient for diagnosis and the risks of underdiagnosis and overtreatment [9:00];
• Regulation of the thyroid axis and conversion of T4 to T3 [13:30];
• Reverse T3 and the metabolic effects of T3 [20:00];
• Thyroid blood tests, assay limitations, and who should be tested [22:45];
• Causes and mimics of hypothyroidism and the criteria for diagnosis [29:00];
• Navigating subclinical hypothyroidism [34:30];
• Treating hypothyroidism with T4 and T3 [37:00];
• Hashimoto's disease, pregnancy, and associated autoimmune risks [42:45];
• Proper timing and administration of thyroid medication [43:45];
• Causes, symptoms, diagnosis, and treatment of hyperthyroidism [45:15];
• Iodine excess, the risks of thyroid-support supplements, and evidence for dietary interventions [53:45];
• A practical framework for evaluating and treating patients who suspect thyroid dysfunction [59:30]; and
• More.

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