Thyrotoxicosis iodide

Amiodarone may induce thyrotoxicosis (2% to 3% of patients) or hypothyroidism. It interferes with type I 5 -deiodinase, leading to reduced conversion of T4 to T3, and iodide release from the drug may contribute to iodine excess. Amiodarone also causes a destructive thyroiditis with loss of thyroglobulin and thyroid hormones. 

Clinical applications include preoperative suppression of thyroid secretion according to Plummer with Lugol s solution (5% iodine + 10% potassium iodide, 50-100 mg iodine/d for a maximum of 10 d). In thyrotoxic crisis, LugoTs solution is given together with thioamides and p-blockers. Adverse effects allergies contraindications iodine-induced thyrotoxicosis. 

Occasionally patients develop a dramatically acute and severe form of thyrotoxicosis which may be life-threatening, termed thyroid crisis or thyroid storm. In this condition the patient is at risk of cardiac complications, notably arrhythmia and ventricular failure, and it requires very urgent treatment. It is essential to use high doses of anti-thyroid drugs, and PTU is often preferred for this, particularly because of its fast absorption. Iodides or ipodate are often... 

Lithium inhibits thyroidal incorporation of L into Tg, as well as the secretion of thyroid hormones, but it does not inhibit the activity of the Na+-I symporter or the accumulation of I within the thyroid. Lithium offers no particular advantage over drugs of the thionamide class but may be employed for temporary control of thyrotoxicosis in patients who are allergic to both thion-amides and iodide. 

Tincture of iodine (aqueous iodine oral solution, Lugol s solution) is a solution of iodine 5 % plus potassium iodide 10% in water, which is used to reduce the vascularity of the thyroid gland in thyrotoxicosis before surgery. 

In patients with hyperthyroidism, potassium iodide is used in the treatment of thyrotoxicosis and to decrease the vascularity of the thyroid before the thyroid gland is surgically removed. Potassium iodide is... 

Potassium iodide plus iodine (Lugol s solution) possible use in thyrotoxicosis used pre-operatively —>4- gland size, fragility, and vascularity... 

Short-term administration of iodide will not harm the fetus. Propylthiouracil may be considered for less severe thyrotoxicosis occurring during pregnancy. The answer is (A). 

The overall inhibitory effect of high doses of iodide on thyroid function tends to decrease over several weeks, which led to the abandonment of iodine treatment of thyrotoxicosis (Harden et ai, 1964), except for the temporary use of Lugol before surgery to reduce thyroid blood flow. 

The chapter includes a section on the metabolism of iodate, since in the case of iodate toxicokinetics plays an important role in the toxicological evaluation. We have scanned the literature and looked at the regulatory status of iodate in the United States, Europe and Switzerland. The chapter will not deal with iodine-induced thyrotoxicosis, since this is a problem of iodine supplementation in general, whether by iodate or iodide. 

Perchlorate, which competitively inhibits the uptake of iodide, has been used in both diagnosis and treatment of thyroid disease. In continental Europe, perchlorate has been used for surgical preparation and in the long-term treatment of thyrotoxicosis. In the United States, the use of perchlorate was drastically curtailed after aplastic anemia and severe renal damage were reported following its use. 

Iodides have. several poorly understood actions on the thyroid. They inhibit organitication and hormone release. In addition, iodide de-crca.scs the size and vascularity of the hyperplastic gland, effects which are useful in the preparation of patients for thyroidectomy. In phamia-cological dose.s. the main effect of iodides is to inhibit hnmtone release (possibly by inhibition of thywglobulin proteolysis) and. because thyrotoxic symptoms are reduced relatively quickly (2 7 days), iodine is valuable in the treatment of thyrotoxic crisis ( thyroid storm —a life-threatening acute exacerbation of all the symptoms of thyrotoxicosis). Iodine caimoi be used for the long-term treatment of hyperthyroidism because its antithyroid action tends to diminish. 

The pharmacological interaction of altered thyroid function with lithium and iodides would appear to be established. However, the clinical use of iodides is now very limited (mostly to the pre-operative treatment of thyrotoxicosis). It is therefore unlikely that iodides will be used in patients on lithium. Where countries are adopting iodization programmes to prevent iodine deficiency, there may be an increased risk of clinical hypothy-... 

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