Thyroid Issues

Question 1

What is the primary screening test for hypothyroidism, and what level indicates primary hypothyroidism?

Answer 1

TSH is the primary screening test. Elevated TSH indicates primary hypothyroidism.

Question 2

How do lab values (TSH and Free T4) differ between primary and secondary hypothyroidism?

Answer 2

Primary Hypothyroidism: High TSH, Low Free T4

Secondary Hypothyroidism: Low TSH, Low Free T4

Question 3

What lab finding confirms that hypothyroidism is due to Hashimoto’s thyroiditis?

Answer 3

Elevated Anti-TPO antibodies (and possibly elevated anti-thyroglobulin antibodies).

Question 4

In early Hashimoto’s disease, can TSH be normal?

Answer 4

Yes. In early stages, TSH may be normal or slightly elevated, and Free T4 may still be normal (subclinical hypothyroidism).

Question 5

What is the hallmark lab pattern for hyperthyroidism?

Answer 5

Low or undetectable TSH with elevated Free T4 and/or Free T3.

Question 6

What antibody test is used to confirm Graves’ disease?

Answer 6

TSI (Thyroid-Stimulating Immunoglobulin). It is highly specific for Graves’.

Question 7

How does the Radioactive Iodine Uptake (RAIU) test differ between Graves’ disease and thyroiditis?

Answer 7

Graves’ disease: Elevated RAIU

Thyroiditis: Low RAIU (due to leakage of hormones from inflammation, not overproduction)

Question 8

What are the key clinical differences between Graves’ disease and other causes of hyperthyroidism?

Answer 8

Graves’ disease presents with:

Exophthalmos (bulging eyes)

Pretibial myxedema (skin thickening)

Diffuse goiter
These are NOT seen in toxic multinodular goiter or thyroiditis.

Question 9

What is the lab pattern in Tertiary Hypothyroidism (hypothalamic origin)?

Answer 9

Low TRH, Low TSH, Low Free T4.

Question 10

A patient has low TSH and low Free T4. Is this primary, secondary, or tertiary hypothyroidism?

Answer 10

Secondary hypothyroidism (pituitary failure) or tertiary (hypothalamic failure). Differentiating requires TRH testing or MRI.

Question 11

What lab pattern is seen in subclinical hypothyroidism?

Answer 11

Elevated TSH, but normal Free T4.

Question 12

What lab pattern is seen in subclinical hyperthyroidism?

Answer 12

Low TSH, but normal Free T4 and Free T3.

Question 13

In which condition would you expect elevated Anti-TPO antibodies and elevated TSH?

Answer 13

Hashimoto’s thyroiditis (most common cause of primary hypothyroidism in iodine-sufficient areas).

Question 14

A patient has hyperthyroidism with a diffusely enlarged thyroid, exophthalmos, and elevated TSI. What is the diagnosis?

Answer 14

Graves’ disease.

Question 15

What lab pattern distinguishes thyroiditis from Graves’ disease in a hyperthyroid patient?

Answer 15

Both have low TSH and high T4/T3, but:

Graves’: Elevated RAIU, positive TSI

Thyroiditis: Low RAIU, negative TSI

Question 16

What is the most common cause of hypothyroidism worldwide?

Answer 16

Iodine deficiency.
(Note: In iodine-sufficient areas, it’s Hashimoto’s.)

Question 17

What is the most common cause of hyperthyroidism?

Answer 17

Graves’ disease.

Question 18

What is the difference in TSH levels between primary hyperthyroidism and secondary hyperthyroidism (rare)?

Answer 18

Primary hyperthyroidism: Low TSH

Secondary hyperthyroidism: High TSH (due to TSH-secreting pituitary tumor)