Thyroid Emergencies And The Acute Take. Dr Sutapa Ray. Consultant Endocrinologist. Harrogate And District Foundation Trust.

Transcription

1 Thyroid Emergencies And The Acute Take Dr Sutapa Ray. Consultant Endocrinologist. Harrogate And District Foundation Trust.

2 Lesson Plan : Case based discussions Acute illness. Thyroid storm Drugs Amiodarone Pregnancy

3 Thyroid Follicle

4 Thyroid Hormone Synthesis

5 Peripheral Circulation and Conversion T3 & T4 binds to globulin (TBG), transthyretin & albumin. Only free hormone is biologically active. T4 converted to T3 ( potent) and reverse T3 (inactive).

6 Central Regulation Hypothalamus Pituitary Thyroid- Axis

7 Interpreting TFTs Primary Hypothyroidism T3 and T4 TSH Secondary Hypothyroidism TSH T3 and T4 Primary Hyperthyroidism T3 and T4 TSH Secondary Hyperthyroidism TSH T3 and T4

8 Peripheral regulation of hormone production T4 to T3 conversion Illness Nutrition Drugs Propylthiouracil Glucocorticoids Beta blockers

9 72 yr male. Smoker, COPD, IHD. David Admitted with pneumonia and dehydration Noted tachycardia TSH < 0.05 miu/ l ( miu/l)

10 David : Management? TSH :- < 0.05 miu/l ( miu/l) Supressed T3 :- 1.6 pmol/l ( pmol/l) Low T4 : pmol/l (10-20 pmol/l) Low normal

11 TFTs in non-thyroidal illness :- Sick euthyroid T3 : reduced peripheral conversion T4 : normal or reduced or spuriously high. TSH : normal or reduced. rt3: increased.

12 TFTs in acute illness DO NOT check unless strong suspicion. Pyrexia, tachycardia, altered mental ( not responding to therapy) AND History of thyroid disease / Recent exposure to iodine contrast medium. ( Exception acute tachy-arrhythmias.) TSH alone inadequate.? Protective to reduce catabolism. Supplements of no benefit.

13 45 yr old Admitted with UTI and acute confusion Temp 40 C, BP 110/60, AF 160. Graves s. Due clinic next week. TSH < 0.05 ( miu/ l) T4 > 70 ( 10-20) pmol, T3 > 35 ( ) pmol. Carbimazole 20 mgs OD, concordant.

14 Thyroid

15 >45 :- highly suggestive :- likely <25 :- unlikely Adapted from: Burch HB, Wartofsky L. Life-threatening thyrotoxicosis. Thyroid storm. Endocrinol Metab Clin North Am 1993; 22:263.

16 Treatment Strategy Reduce hormone production and release Lower conversion of T4 to T3 Block peripheral action Remove circulating hormones Treat precipitating factors Symptomatic treatment

17 Prevent synthesis :- Thionamides Carbimazole/ Propylthiouracil (PTU) Both act to blocks de-novo production. No effect on hormone release. PTU also reduces T4 to T3 conversion. Quicker onset

18 Wolff Chaikoff Effect and Escape: Iodine Temporary inhibition of synthesis. Effect exaggerated in auto-immune disease. Escape in 2-4 weeks. Lugol s Iodine: An hour after thionamides. Rapidly blocks hormone release Reduces hormone synthesis

19 Prevent peripheral conversion T4 to T3 Glucocorticoids Hydrocortisone 100mgs, IV, TDS Iodinated radio-contrast agent Also blocks hormone release. Give an hour after thionamides Propylthiouracil (PTU)

20 Beta Blockers Propranolol mgs 4-6 hrly Cardio-selective blockers? Calcium channel blockers

21 Bile acid sequestrants Hepatic conjugation Secreted in bile Free hormones released Cholestyramine reabsorption 4 gm, oral, QDS

22 Plasmapheresis :- If all else fails! Removes cytokines, antibodies, T3 and T4 Effective within 2-3 sessions Prepare for urgent surgery

23 Thyroid Storm Life-threatening. Mainly CVS:- Heart failure, arrhythmia Mortality 10-30%. Hormone levels may not be profoundly raised. Precipitating factors Surgery, trauma, infection, parturition, Iodine load. Multi-pronged approach

24 Effect of Amiodarone on Thyroid Hormones

25 Amiodarone and the Thyroid Gland Intrinsic effect T4 to T3 conversion Effect due to iodine content Failure of Wolff Chakoff effect Blocks T3 receptor binding Destructive thyroiditis Jod Basedow effect hormone production as increased substrate (iodine)

26 Amiodarone and Hypothyroidism Wolff Chaikoff Effect - Failure to escape

27 Amiodarone induced Hyperthyroidism Type 1 Type 2 Pre-existing thyroid disease Without known disease. Excess iodine as substrate Direct toxicity Increased T4 and T4 synthesis Excess release of T3 & T4 Thionamides Glucocorticoids

28 Expected changes with Amiodarone?

29 Expected changes with Amiodarone At 0 3 mths T4 rises by 20 to 40 Beyond 3 mths. T4 remains slightly elevated or in the upper normal range. T3 decreases by up to 30 T3 concentrations remain in the low normal range. TSH may exceed the upper limit of normal. TSH normalises

30 Kiran Primi, 6/40 gestation. Vomiting. Dehydration. Recent weight loss. Admitted to Obstetrics for IV fluids. TSH < 0.01 miu/l ( ) T4 22. pmol/l ( ) T3 6.7 pmol/l ( ) Diagnosis? Medication?

31 Thyroid Physiology and Pregnancy hcg and TSH similar structure hcg stimulates TSH receptor As hcg, TSH levels. T4 / T3 transient elevation. Exaggerated in hyperemesis

32 Lisa Para 0, Gravida 2, 9/ 40 gestation. Recent UTI TFTs done earlier TSH 6.5 miu/l ( ) T4 11.2pmol/l ( ) T3 3.8 pmol/l ( ) TPO antibodies elevated. Diagnosis?? Intervention holiday for 3 weeks tomorrow

33 Subclinical Hypothyroidism and Pregnancy TPO antibodies associated with spontaneous miscarriage and preterm labour Treatment with Thyroxine may improve outcomes

34 Pregnancy and pre-existing hypothyroidism T3 and T4 circulate bound to TBG Dose of thyroxine to maintain free hormone level Reduce to usual dose post delivery

35 Summary Acute illness. Thyroid storm Effect of Amiodarone Pregnancy.

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