Thyroid Hormone Biosynthesis

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What is the peak effect time for T3 compared to T4?

24-48 hours for T3 and 6-8 hours for T4

12-18 hours for both T3 and T4

The peak effect time is the same for both T3 and T4

6-8 hours for T3 and 24-48 hours for T4 (correct)

Which hormone is considered to be more active in vitro?

T4

T3 (correct)

Neither T3 nor T4

Both T3 and T4

Which hormone binds more tightly to plasma proteins?

Both T3 and T4 bind equally tightly

T3

Neither T3 nor T4 bind tightly

T4 (correct)

What percentage of T3 is produced by the thyroid gland?

20% (A) Signup and view all the answers

Which thyroid hormone is considered to be four times more potent than the other?

T3 (D) Signup and view all the answers

What is the primary use of Levothyroxine sodium (T4)?

Thyroid replacement and suppression therapy (A) Signup and view all the answers

What is the advantage of levothyroxine in terms of dosing frequency?

Once-daily administration (D) Signup and view all the answers

Why is liothyronine not recommended for routine replacement therapy?

Shorter half-life of 24 hours (B) Signup and view all the answers

What is the primary reason for avoiding liothyronine in patients with cardiac disease?

Greater hormone activity and risk of cardiotoxicity (C) Signup and view all the answers

What is the clinical use of liotrix in treating hypothyroidism?

Cretinism & myxedema (B) Signup and view all the answers

Which type of reaction can result from an overuse of thyroxine?

Thyrotoxicosis (A) Signup and view all the answers

How do anti-thyroid drugs treat hyperthyroidism?

Inhibit thyroid hormone synthesis by binding to TPO (A) Signup and view all the answers

What is the most likely cause of SJ's dry skin, coarse and brittle hair, and lack of energy?

Autoimmune thyroiditis (B) Signup and view all the answers

What screening test is recommended to diagnose hypothyroidism in patients with SJ's symptoms?

TSH with reflex free T4 (A) Signup and view all the answers

What is the definition of subclinical hypothyroidism based on the information provided?

TSH 5-10 mIU/ml (C) Signup and view all the answers

Which of the following conditions is NOT listed as an indication for screening for thyroid disease?

Chronic fatigue (A) Signup and view all the answers

What laboratory finding, in addition to the elevated TSH, confirms the diagnosis of autoimmune thyroiditis (Hashimoto's disease) in SJ's case?

Elevated TPO antibodies (C) Signup and view all the answers

What is the initial treatment for SJ's subclinical hypothyroidism?

Levothyroxine 25mcg daily (B) Signup and view all the answers

What is the primary function of the thyroid gland?

To store and produce thyroid hormones (D) Signup and view all the answers

Which of the following is NOT a dietary source of iodide?

Fruits (A) Signup and view all the answers

What is the recommended daily iodine requirement for pregnant and lactating women?

200 μg (A) Signup and view all the answers

Which of the following statements about iodine and iodide is correct?

Iodine denotes all forms of the element, and iodide denotes only the ionic form (I-) (A) Signup and view all the answers

What is the approximate total body content of iodine in an adult?

30 - 50 mg (D) Signup and view all the answers

Which of the following steps is NOT involved in the synthesis of thyroid hormones?

Deiodination (B) Signup and view all the answers

Which medication is considered the drug of choice for managing thyrotoxicosis?

Methimazole (B) Signup and view all the answers

What symptom should a patient report immediately if experiencing while on methimazole therapy?

Jaundice (A) Signup and view all the answers

How should doses of methimazole be tapered during treatment?

Every month (B) Signup and view all the answers