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Thyroid hormones and Anti-thyroid drugs PROF SATYA 2020

This is an interesting ppt illustrating the Pharmacology of Thyroid hormones and Anti-thyroid drugs for medical and paramedical students...

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Thyroid hormones and Anti-thyroid drugs PROF SATYA 2020

  1. 1. DR. V. SATHYANARAYANAN MBBS., M.D., ACME PROFESSOR OF PHARMACOLOGY SRM MCH & RC, KATTANKULATHUR INDIA
  2. 2.  Thyroxine ( T4 )  Triiodothyronine ( T3 )  Calcitonin
  3. 3.  Iodide uptake  Oxidation  iodination  Coupling  Storage  release  Peripheral conversion of T4 to T3
  4. 4.  Highly bound to plasma proteins  T4 – 90 - 95 % bound with TBG, TBPA, albumin  Only the free hormone available for action  Deiodination, glucuronide / sulfate conjugation occurs at liver  Undergo enterohepatic circulation  Finally excreted in urine
  5. 5.  By TSH from anterior pituitary  Hypothalamus  TRH  anterior pituitary  TSH  Thyroid  T3, T4 ------> inhibits TSH, TRH  Normal secretion of T4  70-90 mcg/day  T3  15-30 mcg/ day
  6. 6.  Combines with specific nuclear thyroid hormone receptors bound to “ thyroid hormone response element”  T3 binds with TR  heterodimerizes with RXR ( Retinoid X receptor )  undergo conformational change  release the corepressor  bind the coactivator   induce gene transcription  production of specific mRNA & specific pattern of protein synthesis  various anatomic and metabolic effects
  7. 7.  Growth and development – ( from tadpole to frog ) particularly nervous system  Intermediary metabolism – enhance lipolysis, lipogenesis  promote glycogenolysis, gluconeogenesis  hyperglycemia  Synthesis of certain proteins but Overall Negative nitrogen balance  calorigenesis- increase BMR, increase O2 consumption
  8. 8.  CVS – increased sensitivity to catecholamines , increased beta receptors  increase heart rate, BP, FOC  hyperdynamic circulation  Nervous system – profound functional effect  Skeletal muscle  GIT – increased propulsive activity  Haemopoiesis – facilitates erythropoiesis  Reproduction – indirect effect, role in maintenance of pregnancy and lactation
  9. 9. T3 T4  Less circulating  Less tightly bound to PP  5 times more potent  Faster acting  Active hormone  More avidly bound to the nuclear receptor  Major circulating hormone  More tightly bound to PP  Less potent  Slowly acting  Less active, transport form , functions as prohormone of T3  Less avidly bound
  10. 10.  Replacement therapy in deficiency states  Cretinism  Adult hypothyroidism – oral levothyroxine 50- 200micrograms daily, for indefinitely, in empty stomach  Myxoedema coma  Nontoxic goiter  Thyroid nodule  Papillary carcinoma of thyroid
  11. 11.  Longer acting  Less risk of angina, arrhythmias, CHF  Converted to T3  Stable  Less costly
  12. 12.  EMERGENCY  Progressive mental deterioration  Drug of choice ---L-thyroxine (T4) 200-500 micrograms or leothyronine 100 micrograms i.v  Followed by 100 mic.g i.v OD till oral therapy  Corticosteroids  Ventilatory , cardiovascular support  Correction of hyponatremia  Glucose
  13. 13.  Drugs used to lower the functional capacity of the hyperactive thyroid gland
  14. 14.  INHIBIT HORMONE SYNTHESIS – Propylthiouracil, methimazole, carbimazole  INHIBIT IODIDE TRAPPING – thiocyanates, Perchlorates, nitrates  INHIBIT HORMONE RELEASE – iodine, iodides of Na, K, organic iodide  DESTROY THYROID TISSUE – Radioactive iodine ( 131 I, 125 I, 123I )
  15. 15.  Bind to thyroid peroxidase and prevents oxidation of iodide  Thereby inhibit iodination of tyrosine residues  Inhibit coupling of iodotyrosine residues to form T3, T4  Thereby inhibit T3, T4 synthesis  Propylthiouracil, carbimazole, methimazole
  16. 16. PROPYLTHIOURACIL CARBIMAZOLE  Less potent  Faster acting  Highly bound to PP  Less pass across placenta, milk  Single dose acts for 4-8 hours  No active metabolite  2-3 daily doses required  Inhibits peripheral conversion of T4 to T3  More potent  Slower acting  Less bound  Large doses pass  12-24 hours  Produce active metabolite  Single daily dose  Does not inhibit
  17. 17.  Hypothyroidism  Goiter  GI intolerance  Skin rashes, urticaria, dermatitis  Joint pain  Agranulocytosis – rare but serious  Loss of hair, graying, Loss of taste, fever, liver damage  Do routine WBC counts
  18. 18.  Grave’s disease – young patients as definitive therapy for 12 months  Toxic nodular goiter- in elderly weak patients  Preoperatively in goiter with hyperthyroidism  Hyperthyroidism in pregnancy and lactation  Along with radioactive iodine  Thyroid storm – propylthiouracil is used
  19. 19.  No surgical risk, scar,  No chances of injury to parathyroids or recurrent laryngeal nerve  Hypothyroidism, if induced, is reversible  Can be used in children and younger adults
  20. 20.  Relapse rate is high  Prolonged treatment , even life long is needed  Drug toxicity  Not suitable for uncooperative patients
  21. 21.  Thiocyanates, perchlorates, nitrates  Inhibit iodide trapping  Toxic - bone marrow, liver, kidney, brain  Not used now
  22. 22.  Fastest acting thyroid inhibitor  Inhibit release of thyroid hormones – thyroid constipation  Reduce T3, T4 synthesis  wolff- Chaikoff effect )  Shrinks thyroid gland, makes it less vascular and firm  May produce thyroid escape later  Available as Lugol’s iodine or as potassium iodide solution  3 drops 3 times a day
  23. 23.  Preoperative preparation for thyroidectomy- given for 10 days before surgery  Thyroid storm – Lugol’s iodine 6-10 drops  As iodized salt to prevent endemic goiter  Protection against radioactivity following a nuclear accident  Antiseptic – tincture iodine
  24. 24.  Acute reaction- in sensitive people- hypersensitivity – swelling of lips, angioedema, fever, joint pain, lymphadenopathy  Chronic overdose – iodism – inflammation of mucous membranes, increased secretions, burning sensation in mouth  Hypothyroidism, goiter  Fetal goiter if given in pregnancy
  25. 25.  Thyroidectomy, I131 are contraindicated  With drugs ---- risk of foetal hypothyroidism, goiter  Low doses of propylthiouracil is preferred  Methimazole also safer
  26. 26.  131 I , 123 I, 125 I  Release beta particles which penetrate 0.5 – 2 mm of tissue  Destroy thyroid tissue  Taken orally as sodium salt of 131 I dissolved in water in a single dose
  27. 27.  Used for diagnosis ( 25 – 100 micro curie ) and  treatment of hyperthyroidism due to grave’s disease or toxic nodular goiter ( 3-6 milli curie )  Palliative therapy for metastatic carcinoma of thyroid after surgery
  28. 28.  Simple  Convenient  Given as outpatient basis  Inexpensive  No surgical risk, of scar, injury to parathyroid, nerves  Once hypothyroidism is controlled Cure is permanent  Treatment of choice after 25 yrs, in patients for whom surgery is contraindicated
  29. 29.  Hypothyroidism – 40-60%  Long latent period of response ( 3 months )  Contraindicated during pregnancy  Risk of thyroid carcinoma  Not suitable for children
  30. 30.  PROPRANOLOL  Blocks manifestations of thyrotoxicosis due to sympathetic overactivity  Inhibit peripheral conversion of T4 to T3  Give only symptomatic relief  Little effect on thyroid function & hypermetabolic state  Used in hyperthyroidism while awaiting response  Alongwith iodide for preoperative preparation  Particularly useful in Thyroid storm
  31. 31.  Emergency in hyperthyroidism  Propranolol 1-2 mg I.V – gives dramatic symptomatic relief, most valuable measure  Propylthiouracil 200- 300 mg orally 6th hourly – reduce T3,T4 synthesis & peripheral conversion  Iopanoic acid 0.5- 1g OD oral – inhibit T3,T4 release and their peripheral conversion  Oral/rectal potassium iodide or Lugol’s iodine 6-10 drops inhibit T4 release
  32. 32.  Hydrocortisone 100mg 8th hourly followed by oral prednisolone – helps to tide over crisis, adrenal insufficiency, inhibits peripheral T4 T3 conversion  If tachycardia is not controlled add diltiazem 60-120 mg BD orally  Anxiolytics  antibiotics  Rehydration  external cooling
  33. 33.  Lithium  Amiodarone  Sulfonamides  Phenytoin  Carbamazepine  Rifampicin
  34. 34.  Thyroid hormones are T3 and T4  They are useful in treating hypothyroidism  Antithyroid drugs decrease thyroid function  They are useful in hyperthyroidism  Propylthiouracil is preferred for emrgencies and in pregnancy, carbimazole for others  Radioactive iodine also can be used for hyperthyroidism  Betablockers are also useful especially in thyroid storm
  • Keerthanak41

    Feb. 12, 2021
  • pandiphd1

    Mar. 9, 2020

This is an interesting ppt illustrating the Pharmacology of Thyroid hormones and Anti-thyroid drugs for medical and paramedical students...

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