In this This Is Why with Dr. Busti pharmacology review, Dr. Busti explains the clinical science behind thyroid hormone replacement therapy — one of the most commonly prescribed yet misunderstood treatments in medicine. Drawing from decades of experience as a nurse, pharmacist, and physician, he unpacks the mechanism of action, feedback regulation, pharmacokinetics, monitoring, and clinical pitfalls of drugs like levothyroxine (T4), liothyronine (T3), and desiccated thyroid. Learn why small dose changes can have big effects, how pregnancy and protein binding alter therapy, and how to manage patients safely in both outpatient and inpatient settings.

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Disclaimer: This content is for educational purposes only and is not intended to provide medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have heard in this content.

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Chapter Table of Contents

00:00 – Intro & Why It Matters
03:30 – Drug Options & Indications (T4, T3, Desiccated)
07:30 – HPT Axis & Feedback Basics
11:30 – Mechanism: Synthesis, Iodine, T4→T3
16:00 – PK & Dosing: Empty Stomach, Half-life, Steady State
21:30 – Special Populations: Pregnancy, Post-Thyroidectomy
26:00 – Side Effects & Clinical Risks
31:00 – Drug Interactions: Absorption, Clearance, Conversion
36:30 – Monitoring, Counseling & Key Takeaways

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