Semester 2 - Endocryn System - Thyroid Gland
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- 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 -
- 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 -
- 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 elevatedExplanation
In the case of iodine deficiency, the thyroid gland is unable to produce sufficient amounts of thyroid hormone. This leads to a decrease in the levels of T4, as it is the primary hormone produced by the thyroid gland. However, the pituitary gland senses the low levels of T4 and tries to compensate by increasing the production of TSH (thyroid-stimulating hormone). Therefore, in a patient with iodine deficiency, the expected results would be T4 reduced and TSH elevated.Rate this question:
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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".Rate this question:
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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 reducedExplanation
In a patient with a benign thyroid adenoma ("toxic nodule"), the adenoma itself is producing excess thyroid hormone (T4), leading to elevated levels of T4. However, the excess thyroid hormone suppresses the production of thyroid-stimulating hormone (TSH) from the pituitary gland, resulting in reduced levels of TSH. Therefore, the expected results in this patient would be T4 elevated and TSH reduced.Rate this question:
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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 that plays a crucial role in thyroid hormone synthesis. It catalyzes the coupling of two molecules of DIT (diiodotyrosine) to form T4 (thyroxine), which is the main form of thyroid hormone produced by the thyroid gland. This process occurs within the thyroglobulin molecule, a protein that serves as a precursor for thyroid hormone synthesis. The correct statement correctly identifies the role of thyroid peroxidase in the synthesis of T4.Rate this question:
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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 destructionExplanation
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, eventually causing hypothyroidism. Autoimmune destruction is the most common cause of Hashimoto's thyroiditis, as it is primarily driven by the body's own immune response rather than external factors such as radiation, surgical removal of the thyroid, or hormonal imbalances like hypopituitarism. Polyglandular failure syndrome is a condition that involves the autoimmune destruction of multiple endocrine glands, including the thyroid, but it is less common compared to Hashimoto's thyroiditis as a standalone cause.Rate this question:
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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 receptorsExplanation
In Grave's disease, enlargement of the thyroid gland is caused by an antibody that stimulates TSH receptors. This antibody binds to the TSH receptors on the thyroid gland, leading to an overproduction of thyroid hormones. This excessive stimulation of the thyroid gland results in the enlargement of the gland and the increased production of thyroid hormones, leading to the symptoms of Grave's disease such as hyperthyroidism.Rate this question:
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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. ThyroxineExplanation
The patient's symptoms, such as tiredness, feeling cold, weight gain, muscle cramps, dry skin, and enlarged thyroid gland, are consistent with hypothyroidism. The blood test results confirm this, as the patient has elevated TSH levels and slightly below normal T3 and T4 levels. Thyroxine is the main hormone produced by the thyroid gland, and administering it can help replace the deficient thyroid hormones and alleviate the symptoms of hypothyroidism. Therefore, the administration of thyroxine is the most likely treatment option for this patient.Rate this question:
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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 colloidExplanation
Thyroid follicles do not include Para follicular cells that release calcitonin into the colloid. Calcitonin is actually produced by C cells, which are located outside of the follicles in the thyroid gland. The other statements are true. Thyroid follicles contain thyroglobulin, they are lined by epithelial cells that vary in appearance with the activity of the gland, they are surrounded by a fenestrated capillary network, and they are stimulated by TSH.Rate this question:
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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 hormoneExplanation
The correct answer is that thyroid follicular cells secrete T4 hormone. This is characteristic of the thyroid gland because the thyroid follicular cells are responsible for producing and secreting thyroid hormones, including T4 (thyroxine). T4 is an important hormone that regulates metabolism and growth in the body. The other statements in the options are incorrect or do not accurately describe the characteristics of the thyroid gland.Rate this question:
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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. LevothyroxineExplanation
After being treated with radioactive iodine, the patient's TSH levels are elevated. This suggests that the radioactive iodine treatment successfully reduced the thyroid hormone levels, leading to an increase in TSH production by the pituitary gland. To normalize the thyroid hormone levels, the patient would most likely be prescribed levothyroxine, a synthetic form of thyroid hormone. Levothyroxine would help replace the deficient thyroid hormone and restore normal thyroid function.Rate this question:
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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. LevothyroxineExplanation
The symptoms described in the question, such as lethargy, respiratory difficulties, hoarse cry, and poor sucking, are indicative of hypothyroidism in a newborn. The physical examination findings of large fontanelles, macroglossia, distended abdomen, cyanotic skin, hypotonia, slow reflexes, and hypothermia further support this diagnosis. Levothyroxine is the appropriate drug in this case as it is a synthetic form of thyroid hormone and can effectively treat hypothyroidism.Rate this question:
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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. LevothyroxineExplanation
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 in the body and help regulate the thyroid function. Potassium iodide is used to treat hyperthyroidism, Propranolol is a beta-blocker that can help manage symptoms of hyperthyroidism, Methimazole is used to treat hyperthyroidism, Loperamide is an anti-diarrheal medication, and Diltiazem is a calcium channel blocker used to treat hypertension and angina.Rate this question:
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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 bloodExplanation
The levels of both T3 and T4 are low in this patient, indicating a deficiency in the proteins that bind to and transport these thyroid hormones. The most likely protein to be deficient in this case is thyroxin-binding globulin (TBG), as it is responsible for binding and transporting the majority of T4 in the blood. The normal TSH levels and normal size of the thyroid gland suggest that the issue lies with the binding and transport of thyroid hormones rather than with the production or secretion of thyroid hormones.Rate this question:
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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. PropylthiouracilExplanation
Propylthiouracil is the correct answer because it is an antithyroid drug that inhibits the enzyme responsible for the conversion of T4 to T3 in the liver. By blocking this conversion, propylthiouracil helps to reduce the levels of the active thyroid hormone, T3, in the body. This drug is commonly used in the treatment of hyperthyroidism to help control the overproduction of thyroid hormones.Rate this question:
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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 levelExplanation
Iodine is necessary for the production of thyroid hormones. In cases of iodine deficiency, the thyroid gland is unable to produce enough thyroid hormones, leading to a decrease in negative feedback to the pituitary gland. This results in an increase in the secretion of thyroid-stimulating hormone (TSH) from the pituitary gland. Elevated TSH levels stimulate the thyroid gland to grow and enlarge, causing a goiter. Therefore, the enlargement of the thyroid gland in chronically iodine-deficient patients is most directly related to the elevated TSH level.Rate this question:
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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 doseExplanation
During pregnancy, the demand for thyroid hormones increases, and the woman's levothyroxine dose may need to be increased to maintain adequate thyroid hormone levels. This is necessary for the normal development of the fetus and to control the symptoms of hypothyroidism. Therefore, increasing the levothyroxine dose is the appropriate modification in therapy in this case.Rate this question:
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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. AgranulocytosisExplanation
Propylthiouracil is an antithyroid medication used to treat hyperthyroidism. Agranulocytosis is a serious toxicity that can occur in patients taking propylthiouracil, although it is rare. Agranulocytosis is a condition characterized by a severe decrease in the number of white blood cells, specifically granulocytes, which are important for fighting off infections. This can lead to a compromised immune system and an increased risk of developing serious infections. Therefore, it is important to monitor patients taking propylthiouracil for signs of agranulocytosis, such as fever, sore throat, or signs of infection, and discontinue the medication if necessary.Rate this question:
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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 cellsExplanation
A high dose of iodides inhibits thyroid hormone release from follicular cells. Iodides are known to interfere with the synthesis of thyroid hormones in the thyroid gland. High levels of iodides can block the uptake of iodine by the follicular cells, which is necessary for the production of thyroid hormones. This inhibition leads to a decrease in the release of thyroid hormones into the bloodstream.Rate this question:
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- 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. LevothyroxineExplanation
Levothyroxine is the most appropriate drug for replacement therapy in a hypothyroid patient because it is a synthetic form of the thyroid hormone thyroxine (T4), which is deficient in hypothyroidism. It helps to restore the levels of thyroid hormone in the body, thereby improving symptoms and restoring normal metabolism. Propranolol, Triiodothyronine, Propylthiouracil, and Lithium are not used for replacement therapy in hypothyroidism.Rate this question:
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.JPG "What is the correct relationship between changes in plasma levels of T3 & T4 and release of TRH and TSH?")
.JPG "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).")
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