Thyroid function test interpretation MCQs With Answer

Thyroid function test interpretation MCQs With Answer is a focused question set designed for M.Pharm students specializing in clinical pharmacy practice. This collection emphasizes real-world interpretation of thyroid laboratory data, including TSH, free and total thyroid hormones, antibody testing, and pitfalls such as assay interference and non-thyroidal illness. The questions progress from foundational physiology to complex scenarios—central hypothyroidism, euthyroid sick syndrome, drug-induced alterations, and laboratory artifacts—helping students integrate pharmacology, pathophysiology, and laboratory medicine. Each MCQ includes concise answer keys to reinforce learning and assist exam preparation for clinical decision-making and therapeutic monitoring in endocrinology.

Q1. Which of the following is the single most sensitive initial screening test for primary thyroid dysfunction in ambulatory adults?

• Free T4 concentration
• Total T4 concentration
• Serum TSH concentration
• Free T3 concentration

Correct Answer: Serum TSH concentration

Q2. A patient has low TSH, normal free T4, and elevated free T3. The most likely interpretation is:

• Primary hypothyroidism
• Subclinical hyperthyroidism
• T3 thyrotoxicosis
• Central hypothyroidism

Correct Answer: T3 thyrotoxicosis

Q3. In central (secondary or tertiary) hypothyroidism, typical laboratory pattern is:

• High TSH, low free T4
• Low or inappropriately normal TSH, low free T4
• Low TSH, high free T4
• Normal TSH, normal free T4

Correct Answer: Low or inappropriately normal TSH, low free T4

Q4. Which medication is most likely to falsely lower serum T4 and T3 by displacing thyroid hormones from binding proteins and increasing free fraction transiently?

• Amiodarone
• Phenytoin
• Heparin
• Carbamazepine

Correct Answer: Heparin

Q5. A postpartum woman has elevated TSH and high anti-TPO antibodies. The most probable diagnosis is:

• Graves disease
• Silent (postpartum) thyroiditis leading to hypothyroidism
• Subclinical hyperthyroidism
• Non-thyroidal illness

Correct Answer: Silent (postpartum) thyroiditis leading to hypothyroidism

Q6. Which lab artifact is commonly responsible for falsely elevated thyroid hormone results in immunoassays due to patient antibodies bridging capture and detection antibodies?

• Biotin interference
• Heterophile antibodies
• Hemolysis
• Lipemia

Correct Answer: Heterophile antibodies

Q7. High-dose biotin supplements can cause which pattern on common biotin-streptavidin based immunoassays for thyroid tests?

• False elevation of TSH, false depression of free T4
• False depression of TSH and false elevation of free T4
• No effect on immunoassays
• Only affects total T4 but not free T4 or TSH

Correct Answer: False depression of TSH and false elevation of free T4

Q8. Which of the following thyroid test patterns best suggests euthyroid sick syndrome (non-thyroidal illness) in a severely ill ICU patient?

• Low TSH, very high free T4, normal rT3
• Low free T3, normal or low free T4, normal or low TSH, elevated reverse T3
• High TSH, low free T4, high free T3
• High anti-TPO antibodies with high free T4

Correct Answer: Low free T3, normal or low free T4, normal or low TSH, elevated reverse T3

Q9. Amiodarone can cause both hypothyroidism and hyperthyroidism. Which mechanism explains amiodarone-induced hypothyroidism?

• Iodine deficiency causing decreased production of thyroid hormones
• Wolff-Chaikoff effect from excess iodine load
• Autoimmune stimulation of TSH receptor
• Increased peripheral conversion of T4 to T3

Correct Answer: Wolff-Chaikoff effect from excess iodine load

Q10. A patient has high total T4, normal free T4, and high TBG. Which is the most likely cause?

• Thyroid hormone overproduction (hyperthyroidism)
• Increased TBG due to estrogen therapy or pregnancy
• Thyroid hormone resistance
• Central hypothyroidism

Correct Answer: Increased TBG due to estrogen therapy or pregnancy

Q11. Reverse T3 (rT3) measurement is most helpful to differentiate which of the following?

• Primary hypothyroidism from secondary hypothyroidism
• Thyroid hormone resistance from TSH-secreting pituitary adenoma
• Euthyroid sick syndrome from true hyperthyroidism
• Graves disease from toxic multinodular goiter

Correct Answer: Euthyroid sick syndrome from true hyperthyroidism

Q12. In interpreting a suppressed TSH with normal free T4 in an elderly asymptomatic patient, the best clinical interpretation is:

• Definite overt hyperthyroidism requiring radioiodine therapy
• Subclinical hyperthyroidism that requires risk assessment and follow-up
• Central hypothyroidism
• Laboratory error only; ignore and do nothing

Correct Answer: Subclinical hyperthyroidism that requires risk assessment and follow-up

Q13. Which antibody test is most useful to confirm autoimmune thyroiditis (Hashimoto’s) in a patient with hypothyroidism?

• TSH receptor antibodies (TRAb)
• Anti-thyroid peroxidase (anti-TPO) antibodies
• Anti-TSH antibodies
• Anti-deiodinase antibodies

Correct Answer: Anti-thyroid peroxidase (anti-TPO) antibodies

Q14. Which scenario is most consistent with a pituitary TSH-secreting adenoma rather than primary hyperthyroidism?

• Low TSH with high free T4 and high T3
• Elevated TSH with elevated free T4 and blunted TSH response to TRH stimulation
• Normal TSH with low free T4
• Suppressed TSH with elevated thyroid receptor antibodies

Correct Answer: Elevated TSH with elevated free T4 and blunted TSH response to TRH stimulation

Q15. Which laboratory finding supports the diagnosis of Graves disease as the cause of thyrotoxicosis?

• High anti-TPO antibodies with low TSH
• Positive TSH receptor-stimulating antibodies (TRAb) with suppressed TSH
• Isolated elevation of reverse T3
• High TBG with normal free T4

Correct Answer: Positive TSH receptor-stimulating antibodies (TRAb) with suppressed TSH

Q16. Which pharmacologic agent is known to decrease TSH secretion and can lead to transient lowering of measured TSH in hospitalized patients?

• Interferon-alpha
• Dopamine or dopamine agonists
• Lithium
• Amiodarone

Correct Answer: Dopamine or dopamine agonists

Q17. For neonatal congenital hypothyroidism screening, most programs measure which analyte from a heel-prick specimen as the primary screen?

• Free T4
• Total T3
• TSH
• Anti-TPO antibodies

Correct Answer: TSH

Q18. A patient on high-dose glucocorticoids shows low free T3 on labs. Which mechanism explains this change?

• Increased thyroidal secretion of T3
• Inhibition of peripheral conversion of T4 to T3
• Increased TSH release from the pituitary
• Enhanced TBG production

Correct Answer: Inhibition of peripheral conversion of T4 to T3

Q19. When free T4 and TSH are discordant and assay interference is suspected, which is the most useful next step to clarify true thyroid status?

• Repeat the same assay on the same laboratory equipment
• Measure total T3 only
• Send sample for measurement of free T4 by equilibrium dialysis or alternate assay method
• Start empiric levothyroxine therapy and reassess

Correct Answer: Send sample for measurement of free T4 by equilibrium dialysis or alternate assay method

Q20. In a patient with suspected thyrotoxic storm, which laboratory pattern would you expect to support the diagnosis (while recognizing clinical assessment is primary)?

• Markedly elevated TSH and low free T4
• Suppressed TSH with markedly elevated free T4 and/or free T3, with possible leukocytosis and elevated liver enzymes
• Normal TSH and normal free T4 but high rT3
• Elevated anti-TPO antibodies only

Correct Answer: Suppressed TSH with markedly elevated free T4 and/or free T3, with possible leukocytosis and elevated liver enzymes

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