All of the following are true about amiadarone induced thyroid dysfunction except?
Answer is B (Hypothyroidism is more common in men): `Amiadarone associated hypothyroidism is more common in women and individual with positive TPO antibodies' Amiadarone is a class III antiarrythmic agent structurally related to thyroid hormone and containing very high amount of iodine. Mechanism of actionQ: Amiadorone inhibits deiodinase activity. Initiation of Amiadarone treatment - Inhibitory effect of iodine on T4 release - Wolff Choikoff effect: Excess iodine transiently inhibit thyroid iodide organification Transient decrease in T4 levels (Hypothyroidism) - Escape from Wolff Choikoff effect (most individuals escape from iodide dependent supression of thyroid) - Inhibition of deiodination (deiodination is required for conversion of T4 to T3.) Enhanced T4 levels Decreased T3 levels / increased rT3 Elevated TSH levels (TSH levels normalize or are slightly suppressed after about 1-3 months) Amiadarone associated hypothyroidism: Involves an inability of thyroid to escape from high iodine load. Consequently amiadarone associated hypothyroidism is more common in women and in individuals with positive TPOQ. Amiadarone associated hypehyroidism: Two types of Amiadarone induces thyrotoxicosis (AIT) are seen - AIT - Type I AIT - Type II Associated with an underlying thyroid abnormality - preclinical gravis - multinodular goitre Associated with individuals with no intrinsic thyroid abnormality Thyroid hormone synthesis becomes excessive as a result of increased iodine exposure - Jod basedow phenomenon Thyrotoxicosis results from drug induced lysosomal activation leading to destruction thyroiditis. This can resolve spontaneously or can occasionally lead to hypothyroidism Increased vascularity is seen on color-flow dopier scan Decreased vascularity is seen on color flow dopler scan IL6 levels are marginally raised. IL6 levels are markedly raised.
Hypehyroidism is common in iodine deficient areas
Hypothyroidism is more common in men
Amiodarone inhibits deiodinase activity
Amiodaraone therapy is associated with initial reduction of serum T4 levels