HYPERTHYROIDISM AND THYROTOXICOSIS

Question 1

Which of the following is the most common cause of thyrotoxicosis?
A. Hashimoto’s thyroiditis
B. Toxic multinodular goiter
C. Graves’ disease
D. Pituitary adenoma

Answer 1

Correct Answer: C. Graves’ disease
Rationale: Graves’ disease accounts for 60–80% of cases of thyrotoxicosis, making it the most common cause of thyroid hormone excess.

Question 2

In Graves’ disease, what is the primary cause of hyperthyroidism?
A. Increased iodine intake
B. Thyroid stimulating immunoglobulins (TSIs)
C. Thyroid hormone resistance
D. Pituitary tumors

Answer 2

Correct Answer: B. Thyroid stimulating immunoglobulins (TSIs)
Rationale: In Graves’ disease, hyperthyroidism is caused by thyroid stimulating immunoglobulins (TSIs) that are synthesized by lymphocytes and stimulate the thyroid gland to produce excess thyroid hormones.

Question 3

Which of the following cytokines is involved in the pathogenesis of Graves’ disease and contributes to extra-ocular muscle swelling?
A. Interleukin-10 (IL-10)
B. Tumor necrosis factor (TNF)
C. Interferon γ (IFN-γ)
D. Both B and C

Answer 3

Correct Answer: D. Both B and C
Rationale: Tumor necrosis factor (TNF) and interferon γ (IFN-γ) are cytokines that play a role in the activation of fibroblasts in the extra-ocular muscles, leading to muscle swelling, which is characteristic of Graves’ ophthalmopathy.

Question 4

Which of the following antibodies is found in up to 80% of cases of Graves’ disease?
A. Thyroid receptor antibodies (TRAb)
B. Thyroid peroxidase (TPO) antibodies
C. Anti-thyroglobulin (Tg) antibodies
D. Both B and C

Answer 4

Correct Answer: D. Both B and C
Rationale: Both thyroid peroxidase (TPO) and thyroglobulin (Tg) antibodies are found in up to 80% of cases of Graves’ disease.

Question 5

In Graves’ disease, what is the consequence of late-stage infiltration of the extra-ocular muscles?
A. Reversible muscle swelling
B. Irreversible muscle fibrosis
C. Complete resolution of symptoms
D. Increased thyroid hormone production

Answer 5

Correct Answer: B. Irreversible muscle fibrosis
Rationale: Late in Graves’ disease, the infiltration of extra-ocular muscles leads to irreversible fibrosis of the muscles, contributing to permanent vision problems like proptosis and diplopia.

Question 6

Which of the following is a complication of Graves’ disease related to increased intra-orbital pressure?
A. Optic neuropathy
B. Hypothyroidism
C. Increased iodine uptake
D. Thyroid storm

Answer 6

Correct Answer: A. Optic neuropathy
Rationale: The increase in intra-orbital pressure caused by swelling of the extra-ocular muscles in Graves’ disease can lead to optic neuropathy, which can result in vision loss.

* increase in intra-orbital pressure can lead to proptosis, diplopia, and optic neuropathy

Question 7

Which of the following is a characteristic feature of apathetic thyrotoxicosis in elderly patients?
A. Increased heart rate and hypertension
B. Subtle or masked symptoms with fatigue and weight loss
C. Severe ocular symptoms like proptosis
D. Intense anxiety and tremors

Answer 7

Correct Answer: B. Subtle or masked symptoms with fatigue and weight loss
Rationale: In elderly patients, thyrotoxicosis may present subtly with fatigue and weight loss, a condition known as apathetic thyrotoxicosis

Question 8

Which of the following neurological manifestations is common in patients with thyrotoxicosis?
A. Hyperreflexia and muscle wasting
B. Fasciculation and muscle hypertrophy
C. Severe seizures and paralysis
D. Increased deep tendon reflexes and tremors

Answer 8

Correct Answer: A. Hyperreflexia and muscle wasting
Rationale: Common neurological manifestations of thyrotoxicosis include hyperreflexia, muscle wasting, and proximal myopathy without fasciculation.

Question 9

Which of the following is a known complication of thyrotoxicosis, particularly in Asian males?
A. Hyperkalemic periodic paralysis
B. Hypokalemic periodic paralysis
C. Hyperthyroid-induced heart failure
D. Hyperglycemia-related paralysis

Answer 9

Correct Answer: B. Hypokalemic periodic paralysis
Rationale: Thyrotoxicosis, particularly in Asian males, is associated with a form of hypokalemic periodic paralysis, a condition characterized by sudden muscle weakness and low potassium levels.

Question 10

In Graves’ disease, what is the characteristic change in the thyroid gland?
A. A diffusely enlarged thyroid, often two to three times its normal size
B. A small, atrophic thyroid gland
C. A localized thyroid nodule
D. Complete absence of thyroid tissue

Answer 10

Correct Answer: A. A diffusely enlarged thyroid, often two to three times its normal size
Rationale: In Graves’ disease, the thyroid gland is usually diffusely enlarged, often two to three times its normal size.

Question 11

Graves’ ophthalmopathy can be present:
A. Only during the hyperthyroid phase of Graves’ disease
B. Exclusively after thyroidectomy
C. In 10% of patients with thyrotoxicosis, even in the absence of hyperthyroidism
D. Only in patients with a family history of Graves’ disease

Answer 11

Correct Answer: C. In 10% of patients with thyrotoxicosis, even in the absence of hyperthyroidism
Rationale: Graves’ ophthalmopathy occurs in 10% of patients with thyrotoxicosis even in the absence of hyperthyroidism. In most cases, it occurs within the year before or after the diagnosis of thyrotoxicosis.

Question 12

The earliest symptoms of Graves’ ophthalmopathy typically include:
A. Severe loss of vision
B. Sensation of grittiness, eye discomfort, and excessive tearing
C. Periorbital edema and scleral injection
D. Complete blindness

Answer 12

Correct Answer: B. Sensation of grittiness, eye discomfort, and excessive tearing
Rationale: The earliest symptoms of Graves’ ophthalmopathy include a sensation of grittiness, eye discomfort, and excessive tearing. Later symptoms may include proptosis and more severe eye problems.

Question 13

What is the most serious complication of Graves’ ophthalmopathy?
A. Periorbital edema
B. Proptosis
C. Compression of the optic nerve leading to vision loss
D. Increased intraocular pressure

Answer 13

Correct Answer: C. Compression of the optic nerve leading to vision loss
Rationale: The most serious manifestation of Graves’ ophthalmopathy is compression of the optic nerve at the apex of the orbit, which can lead to papilledema, peripheral field defects, and, if untreated, permanent vision loss.

Question 14

Which condition is characterized by indurated plaques with a deep pink or purple color and an “orange skin” appearance in patients with Graves’ disease?
A. Thyroid acropachy
B. Pretibial myxedema (thyroid dermopathy)
C. Proptosis
D. Exophthalmos

Answer 14

Correct Answer: B. Pretibial myxedema (thyroid dermopathy)
Rationale: Pretibial myxedema, also known as thyroid dermopathy, occurs in <5% of patients with Graves’ disease and is characterized by indurated plaques with a deep pink or purple color and an “orange skin” appearance, often over the anterior and lateral aspects of the lower leg.

Question 15

Thyroid acropachy, a condition associated with Graves’ disease, is characterized by:
A. Severe muscle weakness and wasting
B. Clubbing of the fingers and toes
C. Edema around the eyes
D. Hyperpigmentation of the skin

Answer 15

Correct Answer: B. Clubbing of the fingers and toes
Rationale: Thyroid acropachy refers to a form of clubbing of the fingers and toes and is found in less than 1% of patients with Graves’ disease.

Question 16

Which of the following is a major side effect of antithyroid drugs?

A) Rash
B) Hepatitis
C) Urticaria
D) Fever

Answer 16

Correct Answer: B) Hepatitis

Rationale: Major side effects of antithyroid drugs include hepatitis (especially with propylthiouracil), cholestasis, vasculitis, and agranulocytosis.

• Minor side effects of antithyroid drugs are rash, urticaria, fever, and arthralgia
• Major side effects include hepatitis (especially with propylthiouracil; avoid use in children) and cholestasis (methimazole and carbimazole); vasculitis; and, most important, agranulocytosis (<1%).

Question 17

What is the recommended treatment for thyroid storm in pregnancy?

A) Radioiodine therapy
B) Carbimazole
C) Propylthiouracil
D) Total thyroidectomy

Answer 17

Correct Answer: C) Propylthiouracil

Rationale: Propylthiouracil is recommended in the first trimester of pregnancy and for conditions like thyroid storm. Methimazole is typically avoided due to the risk of congenital defects. Propylthiouracil is preferred for its safer profile in early pregnancy.

• Propylthiouracil - limited indications for its use to the first trimester of pregnancy, the treatment of thyroid storm, and patients with minor adverse reactions to methimazole.

Question 18

How long after starting treatment with antithyroid drugs should thyroid function tests be reviewed?

A) 1–2 weeks
B) 4–6 weeks
C) 6–8 weeks
D) 10–12 weeks

Answer 18

Correct Answer: B) 4–6 weeks

Rationale: Thyroid function tests and clinical manifestations should be reviewed 4–6 weeks after starting antithyroid treatment, and the dose should be adjusted based on unbound T4 levels.

Question 19

Which of the following drugs is known to inhibit the deiodination of T4 to T3?

A) Methimazole
B) Propylthiouracil
C) Carbimazole
D) Atenolol

Answer 19

Correct Answer: B) Propylthiouracil

Rationale: Propylthiouracil inhibits the conversion of T4 to T3, whereas Methimazole and Carbimazole mainly inhibit thyroid peroxidase (TPO). Atenolol is a beta blocker, which does not affect thyroid hormone metabolism.

Question 20

When is radioiodine treatment generally contraindicated?

A) In the first trimester of pregnancy
B) In patients with mild eye disease
C) In patients with hypothyroidism
D) During the acute phase of thyroid storm

Answer 20

Correct Answer: A) In the first trimester of pregnancy

Rationale: Radioiodine treatment is absolutely contraindicated in pregnancy and breastfeeding. It can cause damage to the fetus, and women should wait at least 6 months after treatment before attempting to conceive.

• Pregnancy and breast-feeding are absolute contraindications to radioiodine treatment
  
  • but patients can conceive safely 6 months after treatment

Question 21

Which of the following is an appropriate management strategy for thyrotoxic periodic paralysis?

A) Increased dose of carbimazole
B) Beta blockers
C) Radioiodine therapy
D) Surgery

Answer 21

Correct Answer: B) Beta blockers

Rationale: Beta blockers, such as propranolol or atenolol, are helpful in controlling adrenergic symptoms, including those seen in thyrotoxic periodic paralysis, while the underlying thyrotoxicosis is being addressed.

Question 22

How should antithyroid drugs be managed in pregnancy?

A) Use of radioiodine throughout pregnancy
B) Use of methimazole/carbimazole throughout pregnancy
C) Propylthiouracil until 14–16 weeks of gestation, then switch to methimazole
D) Discontinuation of antithyroid drugs after 20 weeks of gestation

Answer 22

Correct Answer: C) Propylthiouracil until 14–16 weeks of gestation, then switch to methimazole

Rationale: Propylthiouracil is preferred during the first trimester of pregnancy due to the rare risk of methimazole-induced embryopathy. After 14–16 weeks, methimazole or carbimazole should be used instead, as propylthiouracil is associated with rare hepatotoxicity.

* Propylthiouracil should be used until 14–16 weeks’ gestation because of the association of rare cases of methimazole/ carbimazole embryopathy, including aplasia cutis and other defects, such as choanal atresia and tracheoesophageal fistulae
* However, because of its rare association with hepatotoxicity, propylthiouracil should be limited to the first trimester and then maternal therapy should be converted to methimazole (or carbimazole) at a ratio of 15–20 mg of propylthiouracil to 1 mg of methimazole.

Question 23

Which of the following should be monitored if propylthiouracil is used in treatment?

A) Kidney function tests
B) Liver function tests
C) Thyroid-stimulating hormone (TSH) levels
D) Complete blood count (CBC)

Answer 23

Correct Answer: B) Liver function tests

Rationale: Propylthiouracil has a known risk of hepatotoxicity, and liver function tests should be regularly monitored

Question 24

Which of the following is true about radioiodine therapy?

A) It is effective immediately after the first dose.
B) It should not be used in patients with active moderate to severe eye disease.
C) It does not require pretreatment with antithyroid drugs.
D) It is safe for pregnant women.

Answer 24

Correct Answer: B) It should not be used in patients with active moderate to severe eye disease.

Rationale: Radioiodine therapy should generally be avoided in patients with active moderate to severe eye disease, as it may worsen ophthalmopathy.

• Radioiodine - causes progressive destruction of thyroid cells. It can be used as initial treatment or for relapses after a trial of antithyroid drugs
  
  • small risk of thyrotoxic crisis after radioiodine, which can be minimized by pretreatment with antithyroid drugs for at least a month prior
  • Carbimazole or methimazole must be stopped 2–3 days before radioiodine administration and can be restarted 3–7 days after radioiodine in those at risk of complications from worsening thyrotoxicosis.
  • Propylthiouracil appears to have a prolonged radioprotective effect and should be stopped for a longer period

Question 25

What is the main purpose of administering prednisone during radioiodine treatment?

A) To prevent hepatitis
B) To treat thyroid storm
C) To prevent exacerbation of ophthalmopathy
D) To increase the efficacy of radioiodine

Answer 25

Correct Answer: C) To prevent exacerbation of ophthalmopathy

Rationale: Prednisone is administered to prevent the exacerbation of ophthalmopathy in patients undergoing radioiodine therapy, especially in those with Graves’ disease, and it is tapered over 6–12 weeks after treatment.

• Prednisone, 0.2–0.5 mg/kg per d (depending on ophthalmopathy severity), at the time of radioiodine treatment, tapered over 6–12 weeks, may prevent exacerbation of ophthalmopathy
  
  • but radioiodine should generally be avoided in patients with active moderate to severe eye disease

Question 26

What is the most common trigger for a thyrotoxic crisis/thyroid storm?

A) Hypertension
B) Acute illness (e.g., infection, stroke)
C) Hypothyroidism
D) Pregnancy

Answer 26

Correct Answer: B) Acute illness (e.g., infection, stroke)

Rationale: Thyrotoxic crisis is often triggered by acute illness, such as infection, stroke, or trauma, as well as surgery (especially thyroid surgery) or radioiodine treatment in patients with untreated or partially treated hyperthyroidism.

Question 27

Which medication should be given as the first-line treatment for thyroid storm?

A) Methimazole
B) Propranolol
C) Propylthiouracil (PTU)
D) Hydrocortisone

Answer 27

Correct Answer: C) Propylthiouracil (PTU)

Rationale: Propylthiouracil (PTU) is the first-line treatment for thyroid storm. Large doses of PTU (500–1000 mg loading dose and 250 mg every 4 hours) are given to block thyroid hormone synthesis. If PTU is unavailable, methimazole can be used.

Question 28

What is the purpose of administering stable iodide (SSKI) after propylthiouracil in the treatment of thyroid storm?

A) To block thyroid hormone synthesis via the Wolff-Chaikoff effect
B) To reduce fever and delirium
C) To prevent the conversion of T4 to T3
D) To reduce tachycardia

Answer 28

Correct Answer: A) To block thyroid hormone synthesis via the Wolff-Chaikoff effect

Rationale: Stable iodide (SSKI) is given one hour after the first dose of PTU to block thyroid hormone synthesis through the Wolff-Chaikoff effect. This delay allows the PTU to prevent excess iodine from being incorporated into new thyroid hormones.

Question 29

Which of the following medications is used to control tachycardia and adrenergic symptoms in thyroid storm?

A) Cholestyramine
B) Hydrocortisone
C) Propranolol
D) Antibiotics

Answer 29

Correct Answer: C) Propranolol

Rationale: Propranolol is used to control tachycardia and adrenergic symptoms in thyroid storm. High doses of propranolol also decrease the conversion of T4 to T3, further helping to manage the condition.

Question 30

What is the role of glucocorticoids (e.g., hydrocortisone) in the management of thyroid storm?

A) To prevent iodine incorporation into thyroid hormones
B) To control tachycardia
C) To treat underlying infection
D) To prevent adrenal insufficiency and reduce inflammation

Answer 30

Correct Answer: D) To prevent adrenal insufficiency and reduce inflammation

Rationale: Glucocorticoids, such as hydrocortisone, are used in thyroid storm to prevent adrenal insufficiency and help reduce inflammation. They also have some thyroid hormone-blocking properties, which can aid in managing the condition.

Question 31

What is the recommended dose of propylthiouracil (PTU) for the treatment of thyroid storm?

A) 250 mg every 12 hours
B) 500–1000 mg loading dose, then 250 mg every 4 hours
C) 20 mg every 6 hours
D) 60–80 mg every 4 hours

Answer 31

Correct Answer: B) 500–1000 mg loading dose, then 250 mg every 4 hours

Rationale: The recommended dosing for propylthiouracil in thyroid storm is a large loading dose of 500–1000 mg, followed by 250 mg every 4 hours. This aggressive dosing helps manage the crisis effectively.

Question 32

What is the appropriate time to administer stable iodide (SSKI) after the first dose of propylthiouracil in thyroid storm?

A) Immediately
B) 30 minutes later
C) One hour later
D) Two hours later

Answer 32

Correct Answer: C) One hour later

Rationale: Stable iodide (SSKI) is administered one hour after the first dose of propylthiouracil to block thyroid hormone synthesis via the Wolff-Chaikoff effect. This delay ensures that the PTU has time to prevent the incorporation of excess iodine into new thyroid hormones.

Question 33

What is the primary treatment for severe ophthalmopathy with optic nerve involvement or corneal damage?

A) Oral corticosteroids
B) Pulse therapy with IV methylprednisolone
C) Artificial tears and eye ointment
D) Teprotumumab therapy

Answer 33

Correct Answer: B) Pulse therapy with IV methylprednisolone

Rationale: Severe ophthalmopathy, particularly with optic nerve involvement or corneal damage, requires urgent management. This often involves pulse therapy with high doses of IV methylprednisolone, sometimes in combination with surgical interventions such as orbital decompression.

Question 34

Which of the following medications was approved by the FDA in 2020 for the treatment of severe ophthalmopathy?

A) Methimazole
B) Teprotumumab
C) Propylthiouracil
D) Hydrocortisone

Answer 34

Correct Answer: B) Teprotumumab

Rationale: Teprotumumab is a human monoclonal antibody that received FDA approval in 2020 for the treatment of severe ophthalmopathy. It has shown efficacy in managing the condition and is administered in a specific dosing regimen.

Question 35

What is the recommended dosing regimen for teprotumumab?

A) 20 mg/kg IV every 4 weeks for 6 months
B) 10 mg/kg IV initially, then 20 mg/kg IV every 3 weeks for 21 weeks
C) 500 mg IV weekly for 6 weeks, then 250 mg weekly for 6 weeks
D) Oral administration daily for 12 weeks

Answer 35

Correct Answer: B) 10 mg/kg IV initially, then 20 mg/kg IV every 3 weeks for 21 weeks

Rationale: The recommended dosing regimen for teprotumumab is an initial dose of 10 mg/kg IV, followed by 20 mg/kg IV every 3 weeks for 21 weeks. This regimen has been shown to be effective in treating severe ophthalmopathy.

Question 36

When glucocorticoids are ineffective in treating severe ophthalmopathy, what is the next treatment option?

A) Orbital decompression
B) Pulse therapy with methimazole
C) Teprotumumab therapy
D) Antibiotics

Answer 36

Correct Answer: A) Orbital decompression

Rationale: If glucocorticoids are ineffective, orbital decompression can be used as a next step in the treatment of severe ophthalmopathy. This procedure involves removing bone from the walls of the orbit to relieve pressure and improve symptoms.

Question 37

What is the most common cause of acute thyroiditis?

A) Autoimmune processes
B) Suppurative infection of the thyroid
C) Iodine deficiency
D) Radiation therapy

Answer 37

Correct Answer: B) Suppurative infection of the thyroid

Rationale: Acute thyroiditis is a rare condition caused by a suppurative infection of the thyroid gland

*presents with thyroid pain, often referred to the throat or ears, and a small, tender goiter that may be asymmetric
* Fever, dysphagia, and erythema over the thyroid are common, as are systemic symptoms of a febrile illness and lymphadenopathy
* erythrocyte sedimentation rate (ESR) and white cell count are usually increased
* thyroid function is normal

Question 38

Which laboratory finding is most consistent with acute thyroiditis?

A) Suppressed TSH levels
B) Normal thyroid function tests with increased ESR
C) Elevated free T4 and decreased TSH
D) Positive thyroid antibodies

Correct Answer: B) Normal thyroid function tests with increased ESR

Rationale: In acute thyroiditis, thyroid function tests are typically normal, while inflammatory markers such as the erythrocyte sedimentation rate (ESR) and white cell count are elevated.

Answer 38

Correct Answer: B) Normal thyroid function tests with increased ESR

Rationale: In acute thyroiditis, thyroid function tests are typically normal, while inflammatory markers such as the erythrocyte sedimentation rate (ESR) and white cell count are elevated.

*erythrocyte sedimentation rate (ESR) and white cell count are usually increased
* thyroid function is normal

Question 39

What diagnostic procedure confirms the presence of acute thyroiditis and helps identify the causative organism?

A) Radionuclide uptake scan
B) Fine-needle aspiration (FNA) biopsy
C) Thyroid ultrasonography
D) Serum thyroglobulin measurement

Answer 39

Correct Answer: B) Fine-needle aspiration (FNA) biopsy

Rationale: Fine-needle aspiration (FNA) biopsy in acute thyroiditis shows infiltration by polymorphonuclear leukocytes and allows for culture of the sample to identify the causative organism.

Question 40

What is the typical etiology of subacute thyroiditis?

A) Autoimmune processes
B) Viral infection
C) Bacterial infection
D) Iodine deficiency

Answer 40

Correct Answer: B) Viral infection

Rationale: Subacute thyroiditis, also known as viral or de Quervain’s thyroiditis, is typically triggered by a viral infection, often following an upper respiratory tract infection.

Question 41

Which of the following thyroid changes is characteristic of subacute thyroiditis?

A) Symmetrical enlargement with no tenderness
B) Diffuse lymphocytic infiltration
C) Patchy inflammatory infiltrate with multinucleated giant cells
D) Suppurative infection with polymorphonuclear leukocytes

Answer 41

Correct Answer: C) Patchy inflammatory infiltrate with multinucleated giant cells

Rationale: Subacute thyroiditis shows a patchy inflammatory infiltrate with multinucleated giant cells and disruption of thyroid follicles, often progressing to granulomas and fibrosis.

Question 42

Which of the following describes the typical progression of thyroid function in subacute thyroiditis?

A) Persistent hypothyroidism followed by recovery
B) Euthyroidism throughout the illness
C) Phases of thyrotoxicosis, hypothyroidism, and recovery
D) Sudden thyrotoxicosis with no recovery

Answer 42

Correct Answer: C) Phases of thyrotoxicosis, hypothyroidism, and recovery

Rationale: Subacute thyroiditis typically progresses through three phases: an initial thyrotoxic phase due to hormone release from damaged follicles, a hypothyroid phase as hormone stores are depleted, and a recovery phase where normal thyroid function is restored.

(1) thyrotoxic phase
* In the thyrotoxic phase, T4 and T3 levels are increased, reflecting their discharge from the damaged thyroid cells, and TSH is suppressed
(2) hypothyroid phase
(3) recovery phase

Question 43

Which condition is most commonly associated with silent thyroiditis?

A) Viral infection
B) Autoimmune thyroid disease
C) Iodine deficiency
D) Bacterial infection

Answer 43

Correct Answer: B) Autoimmune thyroid disease

Rationale: Silent thyroiditis, also known as painless thyroiditis, occurs in patients with underlying autoimmune thyroid conditions, such as the presence of TPO antibodies.

Question 44

What laboratory findings are characteristic of silent thyroiditis?

A) Elevated ESR and absence of TPO antibodies
B) Normal ESR and presence of TPO antibodies
C) Positive thyroid-stimulating immunoglobulin (TSI)
D) Increased thyroglobulin levels

Answer 44

Correct Answer: B) Normal ESR and presence of TPO antibodies

Rationale: Silent thyroiditis is characterized by normal ESR (unlike subacute thyroiditis) and the presence of TPO antibodies, reflecting its autoimmune basis.

Question 45

Which class of medications is most likely to cause drug-induced thyroiditis?

A) Beta blockers
B) Immune checkpoint inhibitors
C) Antihistamines
D) Diuretics

Answer 45

Correct Answer: B) Immune checkpoint inhibitors

Rationale: Immune checkpoint inhibitors, as well as cytokines like IFN-α and tyrosine kinase inhibitors, are associated with the development of painless drug-induced thyroiditis.

Question 46

What is the most common cause of chronic thyroiditis?

A) Riedel’s thyroiditis
B) Hashimoto’s thyroiditis
C) Subacute thyroiditis
D) Silent thyroiditis

Answer 46

Correct Answer: B) Hashimoto’s thyroiditis

Rationale: Hashimoto’s thyroiditis is the most common clinically apparent cause of chronic thyroiditis and is an autoimmune disorder often presenting with a firm or hard goiter.

Question 47

Which of the following features is characteristic of Riedel’s thyroiditis?

A) Painful, tender goiter with fever
B) Hard, fixed, painless goiter with compressive symptoms
C) Diffuse, symmetric thyroid enlargement with hyperthyroidism
D) Soft, mobile goiter without compressive symptoms

Answer 47

Correct Answer: B) Hard, fixed, painless goiter with compressive symptoms

Rationale: Riedel’s thyroiditis presents with an insidious, painless, hard, and often asymmetric goiter that can cause compressive symptoms, such as dysphagia or airway obstruction.

Question 48

How is Riedel’s thyroiditis definitively diagnosed?

A) Thyroid ultrasound
B) Fine-needle aspiration (FNA) biopsy
C) Open biopsy
D) Thyroid function tests

Answer 48

Correct Answer: C) Open biopsy

Rationale: Diagnosis of Riedel’s thyroiditis requires an open biopsy, as FNA biopsy is typically inadequate for evaluating the fibrosis and infiltrative process.

Treatment of Riedel’s thyroiditis focuses on surgical relief of compressive symptoms caused by the hard, fixed goiter.

Question 49

What is the recommended approach to thyroid hormone abnormalities in a critically ill patient with SES?

A) Immediate thyroid hormone replacement
B) Treat with T3 and T4 combination therapy
C) Avoid routine thyroid function testing and monitor recovery
D) Administer antithyroid drugs

Answer 49

Correct Answer: C) Avoid routine thyroid function testing and monitor recovery

Rationale: Thyroid function testing is not routinely recommended in acutely ill patients unless thyroid disease is strongly suspected. SES usually resolves with recovery from the underlying illness.

Question 50

Why does reverse T3 (rT3) increase in SES?

A) Excess iodine inhibits T4 metabolism
B) Peripheral conversion of T4 to T3 is impaired
C) TSH secretion is increased
D) Pituitary suppression of TSH leads to higher rT3 production

Answer 50

Correct Answer: B) Peripheral conversion of T4 to T3 is impaired

Rationale: In SES, peripheral 5′-deiodinase activity is reduced, impairing the conversion of T4 to T3 and leading to increased production of rT3.

Question 51

What is the definitive method for diagnosing SES?

A) Positive thyroid-stimulating immunoglobulin (TSI)
B) Thyroid ultrasound showing no abnormalities
C) Normalization of thyroid function tests with clinical recovery
D) High levels of antithyroid antibodies

Answer 51

Correct Answer: C) Normalization of thyroid function tests with clinical recovery

Rationale: SES is often a presumptive diagnosis based on clinical context and lab results. Confirmation occurs when thyroid function normalizes after recovery from the underlying illness.

Question 52

Why is amiodarone associated with thyroid dysfunction?

A) It enhances T4 to T3 conversion.
B) It contains a high concentration of iodine.
C) It stimulates the pituitary to secrete excess TSH.
D) It has no structural similarity to thyroid hormones.

Answer 52

Correct Answer: B) It contains a high concentration of iodine.

Rationale: Amiodarone is 39% iodine by weight, leading to a very high iodine load that can cause thyroid dysfunction, including hypothyroidism or hyperthyroidism.

Question 53

What is a common effect of amiodarone on peripheral thyroid hormone metabolism?

A) Enhanced T3 production
B) Suppression of TSH secretion
C) Inhibition of T4 to T3 conversion
D) Increased TSH receptor sensitivity

Answer 53

Correct Answer: C) Inhibition of T4 to T3 conversion

Rationale: Amiodarone inhibits deiodinase activity, reducing the conversion of T4 to T3 and potentially causing euthyroid hyperthyroxinemia or increased LT4 requirements in hypothyroid patients.

Question 54

What condition might develop in a patient with multinodular goiter (MNG) after starting amiodarone?

A) Hashimoto’s thyroiditis
B) Jod-Basedow effect (iodine-induced thyrotoxicosis)
C) Chronic autoimmune thyroiditis
D) TSH-secreting pituitary adenoma

Answer 54

Correct Answer: B) Jod-Basedow effect (iodine-induced thyrotoxicosis)

Rationale: The high iodine load from amiodarone can induce thyrotoxicosis (Jod-Basedow effect) in predisposed patients, such as those with multinodular goiter or incipient Graves’ disease.

Question 55

What is the primary reason amiodarone-induced thyroid dysfunction can persist even after stopping the drug?

A) It permanently alters thyroid receptor sensitivity.
B) It stimulates irreversible thyroid follicular cell destruction.
C) It is stored in adipose tissue, causing high iodine levels to persist.
D) Its metabolites permanently inhibit thyroid hormone synthesis.

Answer 55

Correct Answer: C) It is stored in adipose tissue, causing high iodine levels to persist.

Rationale: Amiodarone is lipophilic and stored in adipose tissue, resulting in persistently high iodine levels for over 6 months after discontinuation.

Question 56

What is the primary mechanism underlying Type 1 amiodarone-induced thyrotoxicosis (AIT)?

A) Destructive thyroiditis caused by lysosomal activation.
B) Suppression of TSH by increased iodine levels.
C) Excessive thyroid hormone synthesis due to increased iodine exposure.
D) Impaired T4 to T3 conversion caused by amiodarone metabolites.

Answer 56

Correct Answer: C) Excessive thyroid hormone synthesis due to increased iodine exposure.

Rationale: Type 1 AIT occurs in individuals with underlying thyroid abnormalities (e.g., nodular goiter or preclinical Graves’ disease) and results from excessive thyroid hormone synthesis due to the iodine load (Jod-Basedow phenomenon).

Question 57

Which diagnostic modality helps differentiate between Type 1 and Type 2 AIT?

A) Thyroid scintigraphy.
B) Color-flow Doppler ultrasonography.
C) TSH receptor antibody (TRAb) testing.
D) Reverse T3 levels.

Answer 57

Correct Answer: B) Color-flow Doppler ultrasonography.

Rationale: Color-flow Doppler ultrasonography reveals increased vascularity in Type 1 AIT, reflecting increased hormone synthesis, while Type 2 AIT shows decreased vascularity due to destructive thyroiditis.

Question 58

Which of the following is a first-line treatment option for Type 2 AIT?

A) Methimazole.
B) Potassium perchlorate.
C) Glucocorticoids.
D) Radioactive iodine.

Answer 58

Correct Answer: C) Glucocorticoids.

Rationale: Type 2 AIT is caused by a destructive thyroiditis and responds to glucocorticoids like prednisone (40 mg daily), which help reduce thyroid inflammation.

Question 59

What is the most definitive treatment option for severe or refractory AIT when other treatments fail?

A) High-dose glucocorticoids.
B) Near-total thyroidectomy.
C) Radioactive iodine therapy.
D) Discontinuation of amiodarone.

Answer 59

Correct Answer: B) Near-total thyroidectomy.

Rationale: Near-total thyroidectomy rapidly reduces thyroid hormone levels and is the most effective long-term solution, especially for severe or refractory cases of AIT, if the patient can safely undergo surgery.