Management of Thyrotoxicosis

A brief review of the various investigations and treatment modalities available for Thyrotoxicosis.

1. Management of Thyrotoxicosis Ahmed Ali Khan Final year MBBS 2011-12 Batch JSS Medical College, Mysore

2. Investigations

3. Thyroid Function Tests Serum T 3 or T 4 levels are very high. TSH is very low or undetectable. (Normal T 3 – 3-9 pmol /L) (Normal T 4 – 8-26 pmol /L) If eye signs are present along with the above values, then other tests are generally not needed.

4. Radioisotope study An 123 I or 131 I uptake and scan should be performed. An elevated uptake shows ‘ hot areas or nodules ’. Grave’s disease shows diffuse uniform over-activity. It also helps to differentiate it from other causes of hyperthyroidism.

5. Antibodies Anti- Tg and anti-TPO antibodies are elevated in up to 75% of patients. Elevated TSH-R or thyroid-stimulating antibodies ( TSAb ) are diagnostic of Graves' disease and are increased in about 90% of patients

6. Other Investigations ECG to look for cardiac involvement. TRH estimation. Total count and neutrophil count are very essential as anti-thyroid drugs may cause agranulocytosis .

7. Management

8. Thyrotoxicosis may be treated by any of 3 treatment modalities — Antithyroid drugs Surgery Radioiodine Therapy 131 I

9. Anti Thyroid Drugs Indicated in children, pregnant women and young adults. Drugs help maintain euthyroid state for a long time in hope of spontaneous remission and prepare the patient for surgery.

10. Anti Thyroid Drugs Carbimazole , Propyluracil , Methimazole etc are some of the commonly used drugs. B adrenergic blockers – Ex : Propranolol In pregnant women – propylthiouracil is preferred

11. Anti Thyroid Drugs Lugol’s Iodine (5% iodine + 10% potassium iodide) – decreases the vascularity of the gland only used as immediate preoperative measure. 10-30 drops/day for 10 days(makes the thyroid firm and easier to handle during surgery) Others – Lithium carbonate, Reserpine , potassium perchlorate

12. Anti Thyroid Drugs Pros : no surgery and no use of radioactive Cons : prolonged t/t and failure rate about 50%. May also cause aplastic anemia, agranulocytosis , hair loss and liver damage. Poor prognosis : large gland size, severity of disease nad TSH- Rab levels.

13. Surgical Treatment Indications Failure of drug therapy Toxic nodular goitre Autonomous toxic nodule Suspected malignancy Grave’s disease in children Very large goitre ( substernal / intrathoracic )

14. Surgical Treatment Subtotal thyroidectomy – both lobes with isthmus are removed and tissue equivalent to pulp of finger is retained at the lower pole of both the lobes.(5-8 grams) Hemithyroidectomy – done for autonomous nodule. Here, entire lateral lobe with the isthmus is removed. Total Thyroidectomy – Preferred in Grave’s disease to achieve lowest relapse rate.

15. Surgical Treatment Pros – Rapid cure and high cure rate, problems associated with radioiodine therapy can be avoided. Surgery also provides tissue for biopsy. Coexisting parathyroid Ca can be removed if present. Only choice for very large retrosternal toxic thyroid. Cons – Recurrence in 5% cases , Thyroid insufficiency in (20-45%) and the generally encountered complications of surgery itself.

16. Radioactive Iodine Therapy ( 131 I) Destroys thyroid cells and reduces mass of thyroid tissue below a critical level by ablation. Indications Primary Thyrotoxicosis after 45 years Autonomous toxic nodule Recurrent Thyrotoxicosis

17. Radioactive Iodine Therapy ( 131 I) Usual dosage is 160 microcurie /gm of thyroid Patient is first made euthyroid by anti-thyroid drugs. Then discontinued for 5 days after which oral radioiodine therapy is initiated. Once the preferred dosage is achieved, radioiodine therapy is stopped. Then anti-thyroid drugs are started after 7 days and continued for 8 weeks.

18. Radioactive Iodine Therapy ( 131 I) It normally takes about 3 months to get full response. Additional 1-2 doses of radioiodine may be required. Due to the pre and post radioiodine therapy dosage of anti-thyroid drugs the patient may go into a state of hypothyroidism. This can be tackled by a maintenance dose of L- thyroixine 0.1mg daily.

19. Radioactive Iodine Therapy ( 131 I) Pros – No Surgery, No prolonged drug therapy and a cure rate of about 90% Cons – Availabilty of services, necessity of proper regular follow up and more importantly, it may cause genetic mutation in younger individuals and thereby predisposing them to various malignancies. Hence, only useful in older adults(>45years).

20. Thank you and have a great day!