Thyroid

Question 1

What are the two main hormones produced by the thyroid gland?

Answer 1

Thyroxine (T4) and Triiodothyronine (T3).

Question 2

What is the primary function of thyroid hormones?

Answer 2

They regulate cell differentiation, organogenesis, thermogenesis, and metabolic homeostasis.

Question 3

What is the normal weight range of the thyroid gland?

Answer 3

12–20 grams.

Question 4

What is the role of TSH in thyroid function?

Answer 4

TSH stimulates thyroid hormone synthesis and secretion.

Question 5

What is the classic endocrine feedback loop in thyroid regulation?

Answer 5

Hypothalamic TRH stimulates pituitary TSH, which stimulates thyroid hormone production.

Question 6

What is the first step in laboratory evaluation of thyroid function?

Answer 6

Measure TSH levels to determine if they are suppressed, normal, or elevated.

Question 7

What does a suppressed TSH level (<0.01 mIU/L) typically indicate?

Answer 7

Thyrotoxicosis.

Question 8

What is the difference between thyrotoxicosis and hyperthyroidism?

Answer 8

Thyrotoxicosis is the state of thyroid hormone excess, while hyperthyroidism is caused by excessive thyroid hormone production by the thyroid gland.

Question 9

What are the major causes of thyrotoxicosis?

Answer 9

Graves’ disease, toxic multinodular goiter (MNG), and toxic adenomas.

Question 10

What percentage of thyrotoxicosis cases are caused by Graves’ disease?

Answer 10

60–80%.

Question 11

What is the most common age range for Graves’ disease onset?

Answer 11

Between 20 and 50 years of age.

Question 12

What are the environmental factors associated with Graves’ disease?

Answer 12

Stress, smoking, sudden increases in iodine intake, and certain drugs (e.g., HAART, alemtuzumab).

Question 13

What is the hallmark of Graves’ ophthalmopathy?

Answer 13

Infiltration of extraocular muscles by activated T cells, leading to proptosis and diplopia.

Question 14

What is the most common cardiovascular manifestation of thyrotoxicosis?

Answer 14

Sinus tachycardia.

Question 15

What is apathetic thyrotoxicosis?

Answer 15

A form of thyrotoxicosis in the elderly characterized by fatigue and weight loss, often mistaken for depression.

Question 16

What is the treatment of choice for Graves’ hyperthyroidism?

Answer 16

Antithyroid drugs (e.g., methimazole, propylthiouracil), radioiodine therapy, or thyroidectomy.

Question 17

What is the starting dose of methimazole for hyperthyroidism?

Answer 17

10–20 mg every 8 or 12 hours.

Question 18

What is the role of beta-blockers in thyrotoxicosis?

Answer 18

They control adrenergic symptoms such as tachycardia and palpitations.

Question 19

What is the main complication of radioiodine therapy?

Answer 19

Hypothyroidism due to destruction of thyroid cells.

Question 20

What is thyroid storm?

Answer 20

A life-threatening exacerbation of hyperthyroidism characterized by fever, delirium, and cardiovascular collapse.

Question 21

What is the mortality rate of thyroid storm?

Answer 21

Up to 30% even with treatment.

Question 22

What is the first-line treatment for thyroid storm?

Answer 22

Large doses of PTU (500–1000 mg loading dose) followed by stable iodide and beta-blockers.

Question 23

What is the most common cause of hypothyroidism worldwide?

Answer 23

Iodine deficiency.

Question 24

What is the most common cause of hypothyroidism in iodine-sufficient areas?

Answer 24

Autoimmune disease (Hashimoto’s thyroiditis).

Question 25

What is the hallmark of Hashimoto’s thyroiditis?

Answer 25

Lymphocytic infiltration of the thyroid with germinal center formation and thyroid follicle atrophy.

Question 26

What is the annual risk of developing clinical hypothyroidism in subclinical hypothyroidism with positive TPO antibodies?

Answer 26

About 4%.

Question 27

What is the typical dose of levothyroxine for hypothyroidism?

Answer 27

1.6 μg/kg body weight (usually 100–150 μg/day).

Question 28

What is the goal of levothyroxine therapy in hypothyroidism?

Answer 28

To normalize TSH levels and relieve symptoms.

Question 29

What is myxedema coma?

Answer 29

A life-threatening complication of severe hypothyroidism characterized by reduced consciousness, hypothermia, and metabolic disturbances.

Question 30

What is the mortality rate of myxedema coma?

Answer 30

20–40% despite treatment.

Question 31

What is the initial treatment for myxedema coma?

Answer 31

IV levothyroxine (200–400 μg loading dose) and hydrocortisone (50 mg every 6 hours).

Question 32

What is the role of thyroid ultrasound in thyroid disease?

Answer 32

It helps diagnose nodular thyroid disease and assess suspicious sonographic features (e.g., hypoechoic nodules with microcalcifications).

Question 33

What is the most common sonographic feature of malignant thyroid nodules?

Answer 33

Hypoechoic solid nodules with infiltrative borders and microcalcifications.

Question 34

What is the role of TPO antibodies in autoimmune thyroid disease?

Answer 34

They are present in up to 80% of Graves’ disease and almost all autoimmune hypothyroidism cases.

Question 35

What is the main role of thyroglobulin (Tg) measurement?

Answer 35

To monitor thyroid cancer patients after thyroidectomy.

Question 36

What is the typical radionuclide scan finding in Graves’ disease?

Answer 36

Diffuse, high uptake of tracer.

Question 37

What is the typical radionuclide scan finding in toxic multinodular goiter?

Answer 37

Multiple areas of relatively increased uptake.

Question 38

What is the most common cause of toxic multinodular goiter?

Answer 38

Functional autonomy of thyroid nodules over time.

Question 39

What is the most common symptom of toxic multinodular goiter?

Answer 39

Hyperthyroidism with a nodular thyroid on palpation.

Question 40

What is the treatment for toxic multinodular goiter?

Answer 40

Radioiodine therapy or thyroidectomy.

Question 41

What is the most common cause of hypokalemic periodic paralysis in thyrotoxicosis?

Answer 41

Excess thyroid hormone leading to intracellular potassium shifts.

Question 42

What is the most common ocular manifestation of Graves’ disease?

Answer 42

Grittiness, eye discomfort, and excess tearing.

Question 43

What is thyroid dermopathy?

Answer 43

A noninflamed, indurated plaque with an orange-peel appearance, occurring in <5% of Graves’ disease patients.

Question 44

What is thyroid acropachy?

Answer 44

A form of clubbing found in <1% of Graves’ disease patients.

Question 45

What is the role of glucocorticoids in thyroid storm?

Answer 45

They reduce T4-to-T3 conversion and treat potential adrenal insufficiency.

Question 46

What is the Wolff-Chaikoff effect?

Answer 46

High iodine intake temporarily inhibits thyroid hormone synthesis.

Question 47

What is the most common cause of hypothyroidism in pregnancy?

Answer 47

Autoimmune thyroiditis (Hashimoto’s thyroiditis).

Question 48

What is the recommended levothyroxine dose adjustment during pregnancy?

Answer 48

Increase by up to 45% to maintain normal TSH levels.

Question 49

What is the most common cause of subclinical hypothyroidism?

Answer 49

Autoimmune thyroiditis with mildly elevated TSH and normal T4 levels.

Question 50

What is the treatment for subclinical hypothyroidism with TSH >10 mIU/L?

Answer 50

Levothyroxine therapy to normalize TSH levels.