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Thyroid Diseases

Thyroid Diseases. Steve Orme Leeds. Introduction. Background Basic Principles Clinical Syndromes Summary. Hypothesis Testing?. Appreciate Limitation of Laboratory Investigations Treat ‘Normal Ranges’ with the Disdain they Deserve Avoid Medicine by Proxy Do not Over Investigate.

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Thyroid Diseases

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  1. Thyroid Diseases Steve Orme Leeds

  2. Introduction • Background • Basic Principles • Clinical Syndromes • Summary

  3. Hypothesis Testing? • Appreciate Limitation of Laboratory Investigations • Treat ‘Normal Ranges’ with the Disdain they Deserve • Avoid Medicine by Proxy • Do not Over Investigate

  4. Basic Principles • Too Much Hormone Measure at Nadir Try to Suppress Evaluate Their 24 Hour Secretion Measure the preceding Hormone (Elevated Free T4, Measure TSH)

  5. Basic Principles • Too Little Hormone Measure at Peak Try to Stimulate Measure the preceding Hormone (Low Free T4, Measure TSH)

  6. Basic Principles • Try to Determine Aetiology Supplementary Hormone Tests Immunology *Radiology/ Nuclear Medicine (* Use Sparingly)

  7. Basic Principles • Remember 1 in 20 Blood Investigations Will be ‘Abnormal’ In An Average ‘Normal’ PatientReference Range :- Mean (95 % Confidence Interval) Small Sample Size

  8. Thyroid Disease • Hypothyroidism • Thyrotoxicosis • Thyroid Nodules/ Cancer • Amiodarone Induced Thyroid Disease

  9. Hypothyroidism • Myxoedema • Hashimoto’s Thyroiditis • Post Surgery/Radioactive Iodine Therapy • Secondary/Tertiary

  10. Hypothyroidism • Free T4 & TSH • TPO Antibodies • Investigate possible co-existing Auto-immune Diseases • Thyroid Imaging Not Indicated

  11. Treatment Strategies Dictated by Diagnosis

  12. CBZ Plasma T 1/2 6-8 Hrs Crosses Placenta & Breast Epithelium >10 more Potent than PTU Duration of Action >24 Hrs PTU Plasma T 1/2 1-2 Hrs Minimal Placental & Breast Transfer Duration of Action 12-24 Hrs Graves DiseasePharmacology of CBZ/PTU

  13. Graves DiseaseDrug Therapy (Adverse Effects) • Minor/Common (5-10%) Pruritis Urticarial Rash Arthralgia Fever

  14. Graves DiseaseDrug Therapy (Adverse Effects) • Uncommon Abnormal Taste (CBZ) GI Upset Hypoglycaemia (Anti-Insulin Antibodies)

  15. Graves DiseaseDrug Therapy (Adverse Effects) • Major (Rare or *Very Rare) Agranulocytosis Aplastic Anaemia* Thrombocytopenia* Hepatitis (PTU)* Cholestatic Jaundice (CBZ)* Lupus-like Syndrome*

  16. Graves DiseaseDrug Therapy (Adverse Effects) • Minor Usually Transient • Major (Agranulocytosis) Idiosyncratic. Onset more Likely in the First 3 Months, High-Dose Therapy and the Elderly.

  17. Graves DiseaseDrug Therapy (Dose, Frequency and Duration) • Titration • Block and Replacement Regimen

  18. Graves DiseaseManaging Relapse • Relapse Rate 60% (10 Years Off Rx) • No difference between 6 Months of Block and Replacement Regimen and 18 Months of Titration • Further Relapses Inevitable After First Failed Trial Of Medication.

  19. Graves DiseasePredicting Relapse • Young Patients • Large Goitre • Presence of TAO • High Levels of TSH-receptor Antibody at Diagnosis.

  20. Graves DiseaseManaging Relapses • I131 • Thyroid Surgery • Long-term Low-dose Thionamide Therapy

  21. Radioactive Iodine Therapy • Counsel Patients • Avoid Pre-Treatment with PTU • Special Measures • Carefully Monitor Thyroid Status for at Least 6 Months

  22. Thyroid Surgery • Choose Your Surgeon Carefully • Counsel Patients • Pre-Treatment Mandatory • Special Measures • Carefully Monitor Thyroid and Calcium Status for at Least 6 Months Post OP • Long-term Data Base Follow UP

  23. Thyroid Nodules & Cancer • Nodules are Common Thyroid Cancer is not (80 Cases per year in West Yorkshire) • Refer Palpable nodules • Early Diagnosis Improves Prognosis • Management Should be through an Endocrine Cancer MDT

  24. Thyroid Nodules & Cancer • Prognosis for Most Cases of Well Differentiated Thyroid Carcinoma is Good • Most Patients Require Total-Thyroidectomy , I131 Radio-ablation and TSH Suppressive Doses of T4 • Life Long Specialist Monitoring is Mandatory

  25. Amiodarone • Benzofuranic Derivative • Contains 37% Iodine • 50-100 times RDI

  26. Amiodarone • Inhibits Type I & II 5’- deiodinase • Cytotoxic to Thyroid Cells • Affects Thyroid Autoimmunity • Acts on Thyroid Hormone Receptors

  27. Euthyroid Patients on Amiodarone • Have Elevated Free T4 • Low Normal Total T3 • High Normal or Transiently Elevated TSH

  28. Amiodarone • Pattern of Thyroid Disease is related to Population Iodine Intake • In the UK 2 % AIT 15% AIH

  29. Amiodarone Induced Thyrotoxicosis • Onset Explosive • Median Duration of Therapy 3Yrs • Unexplained Deterioration • Weight Loss • Overt Signs of Thyrotoxicosis Absent

  30. Type I Goitre Present Iodine Uptake & Colour Flow Doppler Increased Type II No Small/Goitre Inflammatory Markers Increased Low Iodine uptake and Colour Flow Doppler Subsequent Hypothyroidism Amiodarone Induced Thyrotoxicosis

  31. Type I Carbimazole Potassium Perchlorate Radioactive Iodine Surgery Type II Prednisolone Surgery Amiodarone Induced Thyrotoxicosis

  32. Amiodarone Induced Hypothyroidism • Females • Pre-existing Autoimmune Thyroid Disease • Positive TPO Antibodies • Treat as Primary Hypothyroidism

  33. Summary • ‘Where Observation is Concerned, Chance Favours Only The Prepared Mind’(Lois Pasteur 1822-95AD)

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