HYPOTHYROIDISM

Question 1

What is the clinical threshold for diagnosing overt hypothyroidism?

A) TSH >5 mIU/L with normal T4 levels.
B) TSH >10 mIU/L with low unbound T4 levels.
C) TSH >2.5 mIU/L with low T3 levels.
D) TSH >15 mIU/L with normal unbound T4 levels.

Answer 1

Correct Answer: B) TSH >10 mIU/L with low unbound T4 levels.

Rationale: Overt hypothyroidism is characterized by a TSH level >10 mIU/L along with low unbound T4 levels. Symptoms of hypothyroidism typically become more evident at this TSH threshold.

Question 2

Which of the following is a distinguishing histological feature of Hashimoto’s thyroiditis?

A) Extensive fibrosis with absent thyroid follicles.
B) Marked lymphocytic infiltration with germinal center formation.
C) Thyroid follicle hyperplasia and colloid accumulation.
D) Granulomatous inflammation with multinucleated giant cells.

Answer 2

Correct Answer: B) Marked lymphocytic infiltration with germinal center formation.

Rationale: Hashimoto’s thyroiditis is characterized by lymphocytic infiltration, germinal center formation, atrophy of thyroid follicles, and oxyphil metaplasia. In contrast, atrophic thyroiditis shows more extensive fibrosis and an absence of follicles, representing the end stage of Hashimoto’s thyroiditis.

Question 3

Which environmental factor is most strongly associated with an increased risk of autoimmune hypothyroidism?

A) High selenium intake.
B) Smoking cessation.
C) Low iodine intake.
D) Chronic alcohol consumption.

Answer 3

Correct Answer: B) Smoking cessation.

Rationale: Smoking cessation transiently increases the incidence of autoimmune hypothyroidism, while high iodine intake and low selenium intake are also associated risk factors. Interestingly, alcohol intake seems to have a protective effect.

Question 4

What is the primary mechanism of thyroid cell destruction in autoimmune hypothyroidism?

A) Complement-mediated lysis by TPO antibodies.
B) Apoptosis induced by CD8+ cytotoxic T cells and cytokines.
C) Direct damage from TSH receptor-blocking antibodies.
D) Necrosis caused by IL-6 and TNF.

Answer 4

Correct Answer: B) Apoptosis induced by CD8+ cytotoxic T cells and cytokines.

Rationale: Thyroid cell destruction in autoimmune hypothyroidism is primarily mediated by CD8+ cytotoxic T cells, with local production of cytokines (e.g., TNF, IL-1, and IFN-γ) rendering thyroid cells more susceptible to apoptosis.

Question 5

Which autoantibodies are clinically useful markers of thyroid autoimmunity?

A) Anti-TSH receptor and anti-thyroid peroxidase (TPO) antibodies.
B) Anti-TPO and anti-thyroglobulin (Tg) antibodies.
C) Anti-thyroglobulin (Tg) and anti-cytokine antibodies.
D) Anti-TSH receptor and anti-reverse T3 antibodies.

Answer 5

Correct Answer: B) Anti-TPO and anti-thyroglobulin (Tg) antibodies.

Rationale: Anti-TPO and anti-Tg antibodies are the most clinically useful markers of thyroid autoimmunity. Anti-TSH receptor antibodies are present in a subset of cases and are associated with blocking TSH receptor activity.

Question 6

What is the primary mechanism causing non-pitting skin thickening (myxedema) in hypothyroidism?

A) Increased carotene accumulation.
B) Excessive epidermal hyperplasia.
C) Increased glycosaminoglycan content in the dermis.
D) Impaired collagen synthesis.

Answer 6

Correct Answer: C) Increased glycosaminoglycan content in the dermis.

Rationale: Myxedema is caused by an increased dermal glycosaminoglycan content, which traps water and leads to skin thickening without pitting.

Question 7

Which cardiovascular abnormality is most commonly seen in hypothyroidism?

A) Tachycardia with reduced ejection fraction.
B) Pericardial effusion with compromised cardiac function.
C) Bradycardia with reduced stroke volume.
D) Hypertrophic cardiomyopathy with arrhythmias.

Answer 7

Correct Answer: C) Bradycardia with reduced stroke volume.

Rationale: Hypothyroidism leads to reduced myocardial contractility and pulse rate, resulting in bradycardia and decreased stroke volume. Pericardial effusions may occur in up to 30% of cases but rarely compromise cardiac function.

Question 8

Which of the following is a hallmark neurological feature of Hashimoto’s encephalopathy?

A) Seizures and focal neurological deficits.
B) Myoclonus and slow-wave activity on EEG.
C) Progressive dementia without other systemic symptoms.
D) Ataxia and dysarthria.

Answer 8

Correct Answer: B) Myoclonus and slow-wave activity on EEG.

Rationale: Hashimoto’s encephalopathy is a steroid-responsive syndrome associated with TPO antibodies, myoclonus, and slow-wave activity on EEG. It is distinct from other neurological conditions and responds to immunosuppressive therapy.

Question 9

Which reproductive abnormality is commonly associated with hypothyroidism in women?

A) Polycystic ovarian syndrome.
B) Anovulatory cycles with menorrhagia.
C) Oligomenorrhea or amenorrhea.
D) Early menopause with infertility.

Answer 9

Correct Answer: C) Oligomenorrhea or amenorrhea.

Rationale: Hypothyroidism can cause oligomenorrhea or amenorrhea, reduced fertility, and an increased risk of miscarriage. This is due to the effects of thyroid hormone deficiency on reproductive hormone regulation.

Question 10

A patient presents with an elevated TSH level but normal unbound T4. What is the next recommended step if the patient is asymptomatic and thyroid peroxidase antibodies (TPOAb) are negative?

A) Initiate T4 treatment.
B) Perform a radionuclide thyroid scan.
C) Monitor with annual follow-up.
D) Evaluate for pituitary disease.

Answer 10

Correct Answer: C) Monitor with annual follow-up.

Rationale: In mild (subclinical) hypothyroidism with no symptoms and negative TPO antibodies, annual follow-up is advised to monitor TSH levels for progression.

Question 11

What condition is suggested by elevated TSH, low unbound T4, and positive TPOAb?

A) Sick euthyroid syndrome.
B) Autoimmune hypothyroidism.
C) Drug-induced hypothyroidism.
D) Central hypothyroidism.

Answer 11

Correct Answer: B) Autoimmune hypothyroidism.

Rationale: Elevated TSH, low unbound T4, and positive TPO antibodies are indicative of autoimmune hypothyroidism

Question 12

If a patient has normal TSH levels but clinical suspicion of pituitary disease, what should be the next step?

A) No further tests.
B) Measure unbound T4 levels.
C) Perform a radionuclide thyroid scan.
D) Test for TPO antibodies.

Answer 12

Correct Answer: B) Measure unbound T4 levels.

Rationale: In suspected pituitary disease, TSH levels alone may not reflect true thyroid function. Measuring unbound T4 is crucial for accurate assessment.

Question 13

In a patient with low TSH and normal unbound T4 levels, what diagnosis should be considered next?

A) Primary hypothyroidism.
B) Pituitary disease.
C) No further tests are required.
D) Central hypothyroidism.

Answer 13

Correct Answer: C) No further tests are required.

Rationale: Normal unbound T4 levels with normal or low TSH typically do not indicate hypothyroidism, so further testing is unnecessary unless clinical suspicion persists.

Question 14

What is the appropriate management for mild hypothyroidism (normal T4 with elevated TSH) in a symptomatic patient with positive TPO antibodies?

A) Annual follow-up without treatment.
B) Initiate T4 treatment.
C) Refer for pituitary function testing.
D) Evaluate for sick euthyroid syndrome.

Answer 14

Correct Answer: B) Initiate T4 treatment.

Rationale: For mild hypothyroidism with symptoms and positive TPO antibodies, T4 treatment can alleviate symptoms and potentially prevent progression to overt hypothyroidism.

Question 15

What is the typical daily replacement dose of LT4 for an adult patient with no residual thyroid function?

A) 0.5 μg/kg body weight
B) 1.6 μg/kg body weight
C) 2.0 μg/kg body weight
D) 3.0 μg/kg body weight

Answer 15

Correct Answer: B) 1.6 μg/kg body weight

Rationale: For patients with no residual thyroid function, the usual replacement dose of LT4 is 1.6 μg/kg body weight, typically amounting to 100–150 μg daily for adults.

Question 16

What initial dose of LT4 is appropriate for adult patients under 60 years old without evidence of heart disease?

A) 25 μg daily
B) 50–100 μg daily
C) 125 μg daily
D) 200 μg daily

Answer 16

Correct Answer: B) 50–100 μg daily

Rationale: Adult patients under 60 years old without heart disease can be started on 50–100 μg of LT4 daily to prevent over-replacement and monitor for response.

Question 17

How long after initiating LT4 therapy or adjusting the dose should TSH levels be measured?

A) 1 week
B) 1 month
C) 2 months
D) 6 months

Answer 17

Correct Answer: C) 2 months

Rationale: TSH responses are gradual and should be assessed approximately 2 months after initiating or adjusting LT4 therapy to evaluate the adequacy of the dose.

Question 18

What is a common cause of elevated TSH levels in a patient taking ≥200 μg of LT4 daily with normal body weight?

A) Underlying Graves’ disease
B) Poor adherence to treatment
C) Excess iodine intake
D) Drug-induced hypothyroidism

Answer 18

Correct Answer: B) Poor adherence to treatment

Rationale: In patients of normal body weight taking ≥200 μg of LT4 per day, an elevated TSH level often indicates poor adherence to treatment rather than insufficient LT4 dosing.

Question 19

If a patient misses an LT4 dose, what is the recommended action?

A) Skip the dose and wait until the next scheduled dose.
B) Take the missed dose immediately, even if it overlaps with the next one.
C) Take two doses of the skipped tablets at once.
D) Discontinue LT4 for a day and restart the regular dose.

Answer 19

Correct Answer: C) Take two doses of the skipped tablets at once.

Rationale: Since T4 has a long half-life (approximately 7 days), missing one dose can be corrected by taking two tablets the next day without disrupting steady-state levels.

Question 20

Which of the following drugs can interfere with LT4 absorption or metabolism?

A) Aspirin and metoprolol
B) Calcium supplements and proton pump inhibitors
C) Warfarin and digoxin
D) Metformin and sulfonylureas

Answer 20

Correct Answer: B) Calcium supplements and proton pump inhibitors

Rationale: LT4 absorption or metabolism can be affected by calcium supplements, proton pump inhibitors, bile acid sequestrants, iron supplements, sevelamer, and other drugs listed. These interactions should be considered in patients with suboptimal TSH control.

Question 21

What is the definition of subclinical hypothyroidism?

A) Overt thyroid hormone deficiency with TSH >10 mIU/L and symptoms of hypothyroidism
B) Biochemical evidence of thyroid hormone deficiency with few or no clinical features of hypothyroidism
C) Normal TSH with low unbound T4 levels
D) Biochemical evidence of thyroid hormone excess without clinical symptoms

Answer 21

Correct Answer: B) Biochemical evidence of thyroid hormone deficiency with few or no clinical features of hypothyroidism

Rationale: Subclinical hypothyroidism is characterized by elevated TSH levels with normal thyroid hormone levels and minimal or no symptoms of hypothyroidism.

Question 22

When is LT4 treatment recommended for patients with subclinical hypothyroidism?

A) When TSH is <5 mIU/L
B) In all cases regardless of TSH levels
C) For women wishing to conceive or who are pregnant, or when TSH >10 mIU/L
D) Only for symptomatic patients, regardless of TSH levels

Answer 22

Correct Answer: C) For women wishing to conceive or who are pregnant, or when TSH >10 mIU/L

Rationale: LT4 is recommended in subclinical hypothyroidism for women planning to conceive, pregnant women, or when TSH exceeds 10 mIU/L due to the potential risk of adverse outcomes.

Question 23

How is treatment initiated in patients with subclinical hypothyroidism?

A) Full replacement dose of LT4 (1.6 μg/kg body weight)
B) Low dose of LT4 (25–50 μg daily)
C) LT4 combined with T3 therapy
D) No treatment; monitoring only

Answer 23

Correct Answer: B) Low dose of LT4 (25–50 μg daily)

Rationale: Subclinical hypothyroidism treatment begins with a low dose of LT4, typically 25–50 μg daily, with the goal of normalizing TSH levels.

Question 24

What is the recommended management for most patients with subclinical hypothyroidism who are asymptomatic and have TSH levels <10 mIU/L?

A) Start LT4 treatment immediately
B) Monitor TSH and symptoms annually
C) Refer for thyroidectomy
D) Administer high-dose LT4

Answer 24

Correct Answer: B) Monitor TSH and symptoms annually

Rationale: Asymptomatic patients with TSH levels <10 mIU/L typically do not require immediate treatment and can be monitored annually for changes in TSH levels or symptom development.

Question 25

What is the recommended TSH target for hypothyroid women planning to conceive?

A) <2.5 mIU/L
B) <5.0 mIU/L
C) <10.0 mIU/L
D) TSH levels are not important prior to conception

Answer 25

Correct Answer: A) <2.5 mIU/L

Rationale: For hypothyroid women planning to conceive, LT4 therapy is adjusted to maintain TSH levels in the normal range but below 2.5 mIU/L to optimize pregnancy outcomes.

Question 26

How frequently should thyroid function be monitored in hypothyroid pregnant women during the first half of pregnancy?

A) Every week
B) Every 4 weeks
C) Every 6–8 weeks
D) Only at the beginning and end of pregnancy

Answer 26

Correct Answer: B) Every 4 weeks

Rationale: Thyroid function should be monitored every 4 weeks during the first half of pregnancy, as thyroid hormone requirements increase significantly during this time.

Question 27

What is the primary reason pregnant women on LT4 therapy should separate their prenatal vitamin or iron supplement intake from LT4?

A) To prevent vitamin overdose
B) To improve iron absorption
C) To avoid interference with LT4 absorption
D) To reduce gastrointestinal side effects

Answer 27

Correct Answer: C) To avoid interference with LT4 absorption

Rationale: Prenatal vitamins and iron supplements can interfere with LT4 absorption, so they should be taken at different times to ensure the effectiveness of LT4 therapy.

Question 28

What is the recommended starting dose of LT4 for elderly patients with hypothyroidism, particularly those with coronary artery disease?

A) 1.6 μg/kg body weight
B) 50–100 μg/day
C) 12.5–25 μg/day
D) No LT4 therapy is recommended

Answer 28

Correct Answer: C) 12.5–25 μg/day

Rationale: Elderly patients, especially those with coronary artery disease, should begin LT4 therapy at a low dose (12.5–25 μg/day) with slow titration to avoid cardiovascular complications.

Question 29

What is the recommended initial dose of intravenous levothyroxine (LT4) in myxedema coma?
A. 50–100 μg
B. 100–200 μg
C. 200–400 μg
D. 1.6 μg/kg per day

Answer 29

Correct Answer: C. 200–400 μg
Rationale: The initial treatment of myxedema coma includes a loading dose of 200–400 μg of LT4 administered intravenously, followed by daily doses based on the patient’s weight and clinical status.

Question 30

Why is liothyronine (T3) often added to LT4 therapy in myxedema coma?
A. To prevent gastrointestinal bleeding
B. To improve adrenal reserve
C. To enhance T4 → T3 conversion, which is impaired in myxedema coma
D. To reduce the risk of infection

Answer 30

Correct Answer: C. To enhance T4 → T3 conversion, which is impaired in myxedema coma
Rationale: In myxedema coma, the conversion of T4 to T3 is impaired, making it beneficial to add liothyronine (T3) for more rapid therapeutic effects. The initial dose is 5–20 μg, followed by smaller maintenance doses.

Question 31

When is external warming recommended for patients with myxedema coma?
A. When the temperature is <35°C
B. When the temperature is <30°C
C. For all patients regardless of temperature
D. Only if respiratory support is not needed

Answer 31

Correct Answer: B. When the temperature is <30°C
Rationale: External warming is recommended only when the patient’s body temperature falls below 30°C. Overheating should be avoided to prevent vasodilation and cardiovascular instability.

Question 32

What is the purpose of administering hydrocortisone in myxedema coma?
A. To treat concurrent infection
B. To manage cardiovascular instability
C. To address impaired adrenal reserve
D. To improve glucose absorption

Answer 32

Correct Answer: C. To address impaired adrenal reserve
Rationale: In profound hypothyroidism, adrenal reserve may be impaired. Hydrocortisone (50 mg every 6 hours) is administered to prevent adrenal insufficiency and manage the stress response.