Block 5 Endo Thyroid Gland MCQ's

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Block 5 Endo Thyroid Gland MCQ

Questions and Answers
  • 1. 

    Thyroid hormones can increase cardiac output.  From the following table, pick the row that correctly lists the mechanisms by which T3 increases cardiac output.  

    • A.

      A

    • B.

      B

    • C.

      C

    • D.

      D

    • E.

      E

    • F.

      F

    • G.

      G

    Correct Answer
    D. D
    Explanation
    The correct answer is D. The mechanisms by which T3 increases cardiac output include increasing heart rate, increasing stroke volume, and enhancing myocardial contractility.

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  • 2. 

    What is the correct relationship between changes in plasma levels of T3 & T4 and release of TRH and TSH?

    • A.

      A

    • B.

      B

    • C.

      C

    • D.

      D

    • E.

      E

    • F.

      F

    Correct Answer
    B. B
    Explanation
    The correct relationship between changes in plasma levels of T3 & T4 and release of TRH and TSH is that an increase in plasma levels of T3 & T4 leads to a decrease in the release of TRH and TSH. This is because T3 & T4 have negative feedback effects on the hypothalamus and pituitary gland, inhibiting the release of TRH and TSH.

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  • 3. 

    A patient presents with signs of hypothyroidism. To investigate the matter, you measure the levels of T4 and TSH. If the patient suffers from iodine deficiency,  you can expect the following results:

    • A.

      T4 reduced, TSH reduced

    • B.

      T4 elevated, TSH reduced

    • C.

      T4 elevated, TSH elevated

    • D.

      T4 reduced, TSH elevated

    • E.

      T4 reduced, TSH normal

    Correct Answer
    D. T4 reduced, TSH elevated
    Explanation
    In cases of iodine deficiency, the thyroid gland is unable to produce enough thyroid hormones, leading to hypothyroidism. T4 (thyroxine) is the main hormone produced by the thyroid gland, and its levels are reduced in hypothyroidism. TSH (thyroid-stimulating hormone) is released by the pituitary gland to stimulate the thyroid gland to produce thyroid hormones. In response to low levels of thyroid hormones, TSH levels are elevated in hypothyroidism as the pituitary gland tries to stimulate the thyroid gland to produce more hormones. Therefore, in cases of iodine deficiency, the expected results would be T4 reduced and TSH elevated.

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  • 4. 

    What is the unique feature of the antibody produced in Graves' disease that stimulates growth of the thyroid gland?

    • A.

      Enhanced secretion of thyroid stimulating hormone (TSH).

    • B.

      Suppression of TSH secretion

    • C.

      Enhanced secretion of adrenocorticotropic hormone (ACTH).

    • D.

      Blockade of the TSH receptor on thyroid follicular cells.

    • E.

      DON’T KNOW THE ANSWER TO THIS QUESTION…..

    Correct Answer
    E. DON’T KNOW THE ANSWER TO THIS QUESTION…..
    Explanation
    THIS QUESTION DID NOT HAVE AN ANSWER "E", BUT THE ANSWER KEY SAYS THE ANSWER IS "E".

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  • 5. 

    A patient presents with signs of hyperthyroidism (thyrotoxicosis).  To investigate the matter, you measure the levels of T4 and TSH. If the patient has a benign thyroid adenoma ("toxic nodule"), you can expect the following results:

    • A.

      T4 reduced, TSH reduced

    • B.

      T4 elevated, TSH reduced

    • C.

      T4 elevated, TSH elevated

    • D.

      T4 reduced, TSH elevated

    • E.

      T4 reduced, TSH normal

    Correct Answer
    B. T4 elevated, TSH reduced
    Explanation
    In a patient with a benign thyroid adenoma ("toxic nodule"), the adenoma produces excessive amounts of thyroid hormone, leading to hyperthyroidism. This causes an elevation in T4 levels. However, since the adenoma is producing excessive thyroid hormone, the body's feedback mechanism tries to suppress the production of thyroid-stimulating hormone (TSH) from the pituitary gland. As a result, TSH levels are reduced. Therefore, in a patient with a benign thyroid adenoma, the expected results would be T4 elevated and TSH reduced.

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  • 6. 

    The concept map below can be used as a basic algorithm for the determination of thyroid dysfunction. In the following table, pick the correct association of I, II, and III with conditions of euthyroidism,  primary hypothyroidism  (1° hypothyroidism),  and secondary hypothyroidism (2° hypothyroidism).

    • A.

      A

    • B.

      B

    • C.

      C

    • D.

      D

    • E.

      E

    Correct Answer
    A. A
  • 7. 

    Which of the following statements regarding thyroid hormone synthesis is correct?

    • A.

      In the thyroid gland, iodine is oxidized by type II deiodinase

    • B.

      Thyroid peroxidase catalyzes the coupling of two DITs to form T4.

    • C.

      Transport of iodide in to the thyroid gland is facilitated by anions such as perchlorate.

    • D.

      Plasma iodide is transported into the thyroid by facilitated diffusion.

    • E.

      Proteolysis of iodinated thyroglobulin is inhibited by TSH.

    Correct Answer
    B. Thyroid peroxidase catalyzes the coupling of two DITs to form T4.
    Explanation
    Thyroid peroxidase is an enzyme found in the thyroid gland that plays a crucial role in the synthesis of thyroid hormones. It catalyzes the coupling of two molecules of diiodotyrosine (DIT) to form thyroxine (T4). T4 is the main form of thyroid hormone produced by the thyroid gland and is later converted to the active form, triiodothyronine (T3), in peripheral tissues. This statement correctly describes the role of thyroid peroxidase in the synthesis of T4, making it the correct answer.

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  • 8. 

    The most common cause of Hashimoto's thyroiditis is

    • A.

      Therapeutic radiation

    • B.

      Thyroid resection

    • C.

      Hypopituitarism

    • D.

      Autoimmune destruction

    • E.

      Polyglandular failure syndrome.

    Correct Answer
    D. Autoimmune destruction
    Explanation
    Hashimoto's thyroiditis is an autoimmune disease where the body's immune system mistakenly attacks the thyroid gland. This leads to inflammation and damage to the thyroid tissue, causing it to become underactive. The term "autoimmune destruction" accurately describes the cause of Hashimoto's thyroiditis, as it highlights the fact that the immune system is responsible for attacking and destroying the thyroid gland in this condition.

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  • 9. 

    In Grave's disease, enlargement of the thyroid gland is caused by

    • A.

      Constitutive activation of the Gs-protein as a result of a somatic mutation

    • B.

      An antibody that stimulates TSH receptors

    • C.

      Abnormally elevated TSH levels

    • D.

      A transport defect for iodine in the membrane of the follicular cell

    • E.

      Reduced feedback inhibition of the thyrotrophs in the pituitary gland

    Correct Answer
    B. An antibody that stimulates TSH receptors
    Explanation
    In Grave's disease, the enlargement of the thyroid gland is caused by an antibody that stimulates TSH receptors. This antibody, known as thyroid-stimulating immunoglobulin (TSI), binds to the TSH receptors on the thyroid gland and mimics the action of TSH. This leads to the overproduction of thyroid hormones, resulting in the enlargement of the thyroid gland. TSI is produced by the immune system and is believed to be the result of an autoimmune response, where the body mistakenly targets its own tissues.

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  • 10. 

    You are working in a Medicins Sans Frontieres clinic in a mountainous region in the South Eastern part of Africa. A 50 year-old female comes to see you complaining of tiredness and a constant feeling of being cold. Despite no change in her dietary habits she and a constant you has gained weight and also suffers frequent muscle cramps. On physical examination, you notice that her skin is dry, and you detect moderate enlargement of the thyroid gland. You measure her pulse and find that it is 52 beats per minute at rest. Her blood pressure is 101/65mmHg. You send a blood sample to Cape Town. The results of these blood tests reveal that serum TSH is elevated, T3 andT4 levels marginally below normal. The patient's serum is negative for TSH receptor antibodies but positive for thyroid antibodies. This patient's symptoms are most likely to be ameliorated by administration of: .

    • A.

      Thyroid stimulating hormone (TSH)

    • B.

      Dietary iodine supplementation

    • C.

      Thyroxine

    • D.

      TSH receptor antibodies

    • E.

      TRH

    Correct Answer
    C. Thyroxine
    Explanation
    The patient's symptoms, such as tiredness, feeling cold, weight gain, and muscle cramps, along with the physical examination findings of dry skin and enlarged thyroid gland, suggest that she is experiencing hypothyroidism. The blood tests reveal elevated TSH levels and marginally below normal T3 and T4 levels, indicating primary hypothyroidism. The positive thyroid antibodies suggest that the patient has an autoimmune thyroid disease, most likely Hashimoto's thyroiditis. The administration of thyroxine, a synthetic form of the hormone T4, would be the appropriate treatment for this patient as it would help to replace the deficient thyroid hormone and alleviate her symptoms.

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  • 11. 

    Which of the following statements about thyroid follicles is FALSE?

    • A.

      They contain thyroglobulin

    • B.

      They are line by epithelial cells that vary in appearance with the activity of the gland

    • C.

      Their lining includes Para follicular cells that release calcitonin into the colloid

    • D.

      They are surrounded by a fenestrated capillary network

    • E.

      They are stimulated by TSH

    Correct Answer
    C. Their lining includes Para follicular cells that release calcitonin into the colloid
    Explanation
    Thyroid follicles do not contain Para follicular cells, which are responsible for releasing calcitonin. Instead, these cells are found in the thyroid gland, but not within the follicles themselves. The other statements are true: thyroid follicles contain thyroglobulin, their lining is made up of epithelial cells that vary in appearance with gland activity, they are surrounded by a fenestrated capillary network, and they are stimulated by TSH.

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  • 12. 

    Which of the following statements is characteristic of the thyroid gland? pharyngeal pouch

    • A.

      It is derived from the 3rd pharyngeal pouch

    • B.

      It secretes parathyroid hormone

    • C.

      Chief cells are involved in the production of calcitonin

    • D.

      Colloid is primarily composed of calcitonin and T3

    • E.

      Thyroid follicular cells secrete T4 hormone

    Correct Answer
    E. Thyroid follicular cells secrete T4 hormone
    Explanation
    The correct answer is that thyroid follicular cells secrete T4 hormone. This is characteristic of the thyroid gland because the follicular cells are responsible for the production and secretion of thyroid hormones, including T4. T4, also known as thyroxine, is an important hormone involved in regulating metabolism and growth in the body.

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  • 13. 

    A 55-year-old woman with thyrotoxicosis was treated with radioactive iodine. One month later, she had elevated TSH levels. Which of the following drugs was she most likely prescribed at this point in time?   

    • A.

      Potassium iodide

    • B.

      Levothyroxine

    • C.

      Diiodotyrosine

    • D.

      Monoiodotyrosine

    • E.

      Reverse triiodothyronine

    Correct Answer
    B. Levothyroxine
    Explanation
    After being treated with radioactive iodine, the woman's TSH levels are elevated. This suggests that her thyroid function is still low and she is experiencing hypothyroidism. The most likely drug prescribed at this point in time would be levothyroxine, which is a synthetic form of the thyroid hormone T4. Levothyroxine is commonly used to replace or supplement the body's own thyroid hormone production in cases of hypothyroidism.

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  • 14. 

    Few days after a normal delivery, a new born baby boy became lethargic, had respiratory difficulties, hoarse cry, and sucks poorly. Physical examination revealed large fontanelles, macroglossia, a distended abdomen, a cyanotic skin, hypotonia, slow reflexes and hypothermia. Which of the following drugs would be appropriate for this baby?

    • A.

      Methimazole

    • B.

      Somatrem

    • C.

      Levothyroxine

    • D.

      Theophylline

    • E.

      Potassium iodide

    • F.

      Prednisone

    Correct Answer
    C. Levothyroxine
    Explanation
    The symptoms described in the question, such as large fontanelles, macroglossia, distended abdomen, and hypotonia, are consistent with congenital hypothyroidism. Levothyroxine is a synthetic form of thyroid hormone and is the treatment of choice for hypothyroidism. Methimazole is used to treat hyperthyroidism, somatrem is a growth hormone, theophylline is a bronchodilator, potassium iodide is used for iodine deficiency, and prednisone is a corticosteroid. Therefore, the most appropriate drug for this baby is levothyroxine.

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  • 15. 

    A 75-year-old woman came to the clinic for her regular checkup. Her only complaints included very dry skin and constipation which she treats with milk of magnesia. She had no other medical problems and took no other medications. Routine laboratory tests are within normal limits except for a TSH of 15 mIU/mL (normal0.5-5.5). Further lab exams indicated the presence of thyroid peroxidase antibodies. Which of the following drug would be appropriate for this patient?

    • A.

      Potassium iodide

    • B.

      Propranolol

    • C.

      Methimazole

    • D.

      Loperamide

    • E.

      Levothyroxine

    • F.

      Diltiazem

    Correct Answer
    E. Levothyroxine
    Explanation
    The patient's elevated TSH levels and presence of thyroid peroxidase antibodies indicate that she has hypothyroidism, specifically Hashimoto's thyroiditis. Levothyroxine is the appropriate drug for this patient as it is a synthetic form of thyroid hormone that can replace the deficient hormone and help regulate the patient's thyroid function. Potassium iodide is used for iodine deficiency, propranolol is a beta-blocker used for hypertension and heart conditions, methimazole is used for hyperthyroidism, loperamide is an anti-diarrheal agent, and diltiazem is a calcium channel blocker used for hypertension and angina.

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  • 16. 

    A routine laboratory test for cardiovascular risk factors in a normal 60-year-old man shows that his levels of both T3 andT4 are only about 20% of normal. TSH is in the normal range, and the thyroid gland is of normal size without palpable masses. There are no clinical signs of abnormal thyroid function.  Which of the following proteins is most likely deficient in this patient?

    • A.

      The TSH receptor

    • B.

      The T3 receptor

    • C.

      Thyroxin-binding globulin in the blood

    • D.

      Thyroglobulin in the thyroid gland

    • E.

      Pendrin

    Correct Answer
    C. Thyroxin-binding globulin in the blood
    Explanation
    In this scenario, the patient's levels of both T3 and T4 are significantly lower than normal, while TSH is within the normal range. This suggests that the thyroid gland is functioning properly, but there may be an issue with the transportation or binding of T3 and T4 hormones in the blood. Thyroxin-binding globulin (TBG) is a protein that binds to T3 and T4 in the blood, allowing for their transport to target tissues. A deficiency in TBG would result in lower levels of bound T3 and T4, leading to the observed laboratory findings. Therefore, the most likely deficient protein in this patient is thyroxin-binding globulin in the blood.

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  • 17. 

    Which of the following drugs can block most effectively the conversion of T4 to T3 by the liver?

    • A.

      Levothyroxine

    • B.

      Diiodotyrosine

    • C.

      TSH

    • D.

      Propylthiouracil

    Correct Answer
    D. Propylthiouracil
    Explanation
    Propylthiouracil is the correct answer because it is an anti-thyroid drug that inhibits the conversion of T4 to T3 by blocking the enzyme responsible for this conversion in the liver. This drug is commonly used in the treatment of hyperthyroidism to reduce the levels of thyroid hormones in the body. Levothyroxine is a synthetic form of T4 and does not block the conversion, while diiodotyrosine and TSH do not have any direct effect on the conversion process.

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  • 18. 

    Iodine deficiency used to be a common cause of thyroid enlargement (goiter) in some parts of the world. Which abnormality in chronically iodine-deficient patients is most directly related to the enlargement of the thyroid gland?  

    • A.

      Reduced activity of thyroperoxidase

    • B.

      Impaired conversion of T4to T3

    • C.

      Reduced level of cAMP in the thyroid follicular cells

    • D.

      An antibody that binds to the TSH receptor in the thyroid gland

    • E.

      Elevated TSH level

    Correct Answer
    E. Elevated TSH level
    Explanation
    Chronic iodine deficiency leads to decreased production of thyroid hormones, which results in elevated levels of thyroid-stimulating hormone (TSH) from the pituitary gland. TSH stimulates the thyroid gland to grow and produce more hormones, leading to the enlargement of the thyroid gland, known as goiter. Therefore, the elevated TSH level is most directly related to the enlargement of the thyroid gland in chronically iodine-deficient patients.

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  • 19. 

    A 28-year-old woman with hypothyroidism has missed her menstrual period this month. Pregnancy test is positive. She has been on levothyroxine for one year. Which of the following modification in her therapy is required for the normal development of the fetus and to control her symptoms?

    • A.

      Increase levothyroxine dose

    • B.

      Substitute levothyroxine dose with triiodothyronine

    • C.

      Decrease levothyroxine dose

    • D.

      Stop therapy with levothyroxine

    Correct Answer
    A. Increase levothyroxine dose
    Explanation
    During pregnancy, the demand for thyroid hormone increases due to the growth and development of the fetus. Therefore, it is necessary to increase the dose of levothyroxine in pregnant women with hypothyroidism to maintain adequate thyroid hormone levels. This will ensure normal development of the fetus and help control the symptoms of hypothyroidism in the mother.

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  • 20. 

    A 37-year-old who presented with symptoms of hyperthyroidism was diagnosed with Grave's disease. He was started on propylthiouracil and propranolol. Which of  the following is a serious toxicity that can occur, though rarely, in patients taking propylthiouracil?

    • A.

      Myopathy

    • B.

      Cardiac arrhythmias

    • C.

      Agranulocytosis

    • D.

      Dry mouth

    • E.

      Weight loss

    Correct Answer
    C. Agranulocytosis
    Explanation
    Propylthiouracil is commonly used to treat hyperthyroidism, including Grave's disease. However, one serious toxicity that can occur, although rarely, is agranulocytosis. Agranulocytosis is a condition characterized by a severe decrease in the number of white blood cells, specifically neutrophils, which are important for fighting off infections. This can increase the risk of developing serious infections. It is important for patients taking propylthiouracil to be aware of this potential side effect and to seek medical attention if they experience symptoms such as fever, sore throat, or other signs of infection.

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  • 21. 

    Which of the following describes the effect of high dose of iodides on thyroid gland?

    • A.

      It blocks the release of THS from pituitary gland

    • B.

      It inhibits thyroid hormone release from follicular cells

    • C.

      It increases the vascularity of thyroid gland

    • D.

      It causes necrosis of thyroid follicular cells

    Correct Answer
    B. It inhibits thyroid hormone release from follicular cells
  • 22. 

    Which of the following drugs is most appropriate to be used for replacement therapy in a hypothyroid patient?

    • A.

      Propranolol

    • B.

      Levothyroxine

    • C.

      Triiodothyronine

    • D.

      Propylthiouracil

    • E.

      Lithium

    Correct Answer
    B. Levothyroxine
    Explanation
    Levothyroxine is the most appropriate drug for replacement therapy in a hypothyroid patient. Hypothyroidism is a condition where the thyroid gland does not produce enough thyroid hormones. Levothyroxine is a synthetic form of the thyroid hormone thyroxine, which helps to restore the levels of thyroid hormones in the body. It is the standard treatment for hypothyroidism and is effective in relieving the symptoms associated with the condition. Other options like Propranolol, Triiodothyronine, Propylthiouracil, and Lithium are not suitable for replacement therapy in hypothyroid patients.

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    Quiz Edited by
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