Thyroid drugs

Thyroid drugs

Thyroid secretes triiodothyronine (T3) and tetraiodothyronine (T4 or thyroxine)

Thyroid hormones preparations:
• eg levothyroxine (T4), liothyronine (T3), liotrix (mixture of T3 & T4)
• indicated for thyroid hormone replacement in hypothyroidism
• lecotyroxime is most commonly used; most is converted to T3 when administered
• adverse effects – tachycardia, arrhythmias, nervousness, sweating, heat intolerance, insomnia, weight loss, thyrotoxicosis (if high dose)

Antithyroid drugs:
Used for hyperthyroidism
Propylthiouracil:
• inhibits thyroid hormone synthesis by preventing oxidation of iodide (can not be incorporated into tyrosine) and prevents the iodinated tyrosines from coupling
• indicated for hyperthyroidism
• adverse effects – agranulocytosis, hypothyroidism

Radioactive iodine (131I):
• used to destroy thyroid tissue in those with hyperthyroidism by emitting beta particles and gamma rays
• hypothyroidism is a frequent complication

Lugols’s solution/strong iodine solution:
• high doses of iodine has a suppressant effect on thyroid
• more effective as a short term measure

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