Block 13 Thyroid Parathyroid Steroid Adrenal MCQ's

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Block 13 Thyroid Parathyroid Steroid Adrenal MCQ

Review of thyroid disorders, steroids, adrenal drugs and parathyroid


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.   Rate of atrial pacemaker depolarization Expression of cardiac Na2+/exchanger Expression of cardiac b-adrenergic receptors Expression of Cardiac Na+,K+-ATPase A Increase Decrease Decrease Increase B Decrease Increase Increase Decrease C Increase Increase Decrease Decrease D Increase Increase Increase Increase E Decrease Decrease Increase Increase F Decrease Increase Decrease Increase G Increase Increase Increase Decrease

    • A. 

      A

    • B. 

      B

    • C. 

      C

    • D. 

      D

    • E. 

      E

    • F. 

      F

    • G. 

      G

    Correct Answer
    D. D
    Explanation
    The correct answer is D. Thyroid hormones increase the expression of cardiac Na+,K+-ATPase. This enzyme is responsible for maintaining the balance of sodium and potassium ions in cardiac cells, which is crucial for normal cardiac function. By increasing the expression of this enzyme, thyroid hormones enhance the ability of the heart to pump blood, leading to an increase in cardiac output.

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  • 2. 

    What is the correct relationship between changes in plasma levels of T3 & T4 and the release of TRH and TSH?   T3 & T4 TRH TSH A Increase Increase Decrease B Decrease Increase Increase C Decrease Decrease Decrease D Increase Increase Increase E Increase Decrease Increase F Decrease Decrease Increase

    • 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 the release of TRH and TSH is that an increase in T3 & T4 levels leads to a decrease in the release of TRH and TSH. This is because T3 & T4 act as negative feedback signals to the hypothalamus and pituitary gland, inhibiting the release of TRH and TSH. Therefore, when T3 & T4 levels are high, the release of TRH and TSH is suppressed, resulting in a decrease in their plasma levels.

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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
    If a patient presents with signs of hypothyroidism and suffers from iodine deficiency, the expected results would be a reduction in T4 levels and an elevation in TSH levels. This is because iodine is necessary for the production of thyroid hormones, including T4. When there is an iodine deficiency, the thyroid gland is unable to produce enough T4, leading to a reduction in its levels. In response to the low levels of T4, the pituitary gland releases more TSH to stimulate the thyroid gland to produce more thyroid hormones, resulting in an elevation in TSH levels.

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  • 4. 

    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 into 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 involved in the synthesis of thyroid hormones. It catalyzes the coupling of two molecules of diiodotyrosine (DIT) to form thyroxine (T4), which is the main form of thyroid hormone produced by the thyroid gland. This process is essential for the production of T4, which is then converted to the active form of thyroid hormone, triiodothyronine (T3), in peripheral tissues. The other statements are incorrect: type II deiodinase is not involved in iodine oxidation, anions such as perchlorate inhibit iodide transport, plasma iodide is transported by active transport, and TSH promotes proteolysis of iodinated thyroglobulin.

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  • 5. 

    Which of the following statements about thyroid follicles is FALSE?

    • A. 

      They contain thyroglobulin

    • B. 

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

    • C. 

      Their lining includes parafollicular 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 parafollicular cells that release calcitonin into the colloid
    Explanation
    Thyroid follicles do not include parafollicular cells that release calcitonin into the colloid.

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  • 6. 

    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 patients with a benign thyroid adenoma (toxic nodule), the adenoma itself produces excessive amounts of thyroid hormone (T4), leading to elevated levels of T4. However, the excessive production of T4 suppresses the release of thyroid-stimulating hormone (TSH) from the pituitary gland, resulting in reduced levels of TSH. Therefore, in this scenario, the expected results would be T4 elevated and TSH reduced.

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  • 7. 

    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).   I II III A Euthyroid 1˚ hypothyroidism 2˚ hypothyroidism B 1˚ hypothyroidism 2˚ hypothyroidism Euthyroid C 1˚ hypothyroidism Euthyroid 2˚ hypothyroidism D 2˚ hypothyroidism Euthyroid 1˚ hypothyroidism E 2˚ hypothyroidism 1˚ hypothyroidism Euthyroid

    • A. 

      A

    • B. 

      B

    • C. 

      C

    • D. 

      D

    • E. 

      E

    Correct Answer
    A. A
    Explanation
    The correct association is A, where I is associated with euthyroidism, II is associated with primary hypothyroidism (1˚ hypothyroidism), and III is associated with secondary hypothyroidism (2˚ hypothyroidism).

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  • 8. 

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

    • 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 it is responsible for producing and secreting thyroid hormones, including T4 (thyroxine). T4 hormone plays a crucial role in regulating metabolism, growth, and development in the body. The other statements are incorrect. The thyroid gland is derived from the 4th pharyngeal pouch, not the 3rd. It does not secrete parathyroid hormone, which is produced by the parathyroid glands. Chief cells are involved in the production of parathyroid hormone, not calcitonin. The colloid in the thyroid gland is primarily composed of thyroglobulin, not calcitonin and T3.

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  • 9. 

    A routine laboratory test for cardiovascular risk factors in a normal 60-year-old man shows that his levels of both T3 and T4 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, indicating a deficiency in the production or availability of thyroid hormones. Since TSH levels are normal and the thyroid gland is of normal size without palpable masses, it suggests that the problem lies outside of the thyroid gland itself. Thyroxin-binding globulin (TBG) is a protein that binds to and transports thyroid hormones in the blood. A deficiency in TBG would lead to decreased levels of T3 and T4 in the blood, explaining the patient's laboratory findings.

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  • 10. 

    Which of the following statements best explains the mechanism of actions of thyroid hormones?

    • A. 

      They inhibit the synthesis of Na+/K+ ATPase in cell membranes

    • B. 

      They modulate transcription of selected genes in the nucleus

    • C. 

      They inhibit assembly of selected ribosomes on the rough endoplasmic reticulum

    • D. 

      They inhibit turnover of selected lipids in the Golgi complex

    • E. 

      They activate the synthesis of lipocortin

    Correct Answer
    B. They modulate transcription of selected genes in the nucleus
    Explanation
    Thyroid hormones are known to modulate transcription of selected genes in the nucleus. This means that they can influence the expression of specific genes by either increasing or decreasing their transcription. By doing so, thyroid hormones can regulate various physiological processes in the body, such as metabolism, growth, and development. This mechanism of action allows thyroid hormones to have widespread effects on different tissues and organs in the body.

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  • 11. 

    Most of the known effects of corticosteroids are mediated by actions on which of the following molecular targets?

    • A. 

      G-protein coupled receptors

    • B. 

      Tyrosine kinase receptors

    • C. 

      Specific nucleotide sequences of the DNA

    • D. 

      Ion channel coupled receptors

    • E. 

      Specific nucleotide sequences of RNA

    • F. 

      Specific nucleotide sequences of ribosomes

    Correct Answer
    C. Specific nucleotide sequences of the DNA
    Explanation
    Corticosteroids primarily exert their effects by binding to specific nucleotide sequences of the DNA. This binding leads to the activation or inhibition of gene transcription, resulting in the production of proteins that mediate the anti-inflammatory, immunosuppressive, and metabolic effects of corticosteroids. This mechanism of action allows corticosteroids to regulate a wide range of physiological processes and modulate the immune response. G-protein coupled receptors, tyrosine kinase receptors, ion channel coupled receptors, specific nucleotide sequences of RNA, and specific nucleotide sequences of ribosomes are not the primary targets for corticosteroid action.

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  • 12. 

    Which of the following actions most likely contributes to the antiinflammatory effects of glucocorticoids?

    • A. 

      Inhibition of ACTH release

    • B. 

      Increased catabolism of prostaglandins

    • C. 

      Increased capillary permeability

    • D. 

      Increased release of interleukin-1

    • E. 

      Induction of lipocortin synthesis

    Correct Answer
    E. Induction of lipocortin synthesis
    Explanation
    Annexin is also known as *** lipocortin.**** Lipocortins suppress phospholipase A2. This is the mechanism by which glucocorticoids (primarily cortisol) inhibit inflammation.

    Annexin A-I seems to be one of the most heavily involved annexins in anti-inflammatory responses. Upon infection or damage to tissues, annexin A-I is believed to reduce inflammation of tissues by interacting with annexin A-I receptors on leukocytes. In turn, the activation of these receptors functions to send the leukocytes to the site of infection and target the source of inflammation directly. As a result, this inhibits leukocyte (specifically neutrophils) extravasation and down regulates the magnitude of the inflammatory response. Without annexin A-I in mediating this response, neutrophil extravasation is highly active and worsens the inflammatory response in damaged or infected tissues. Annexin A-I has also been implicated in apoptotic mechanisms in the cell. When expressed on the surface of neutrophils, annexin A-I promotes pro-apoptotic mechanisms. Alternatively, when expressed on the cell surface, annexin A-I promotes the removal of cells that have undergone apoptosis. Moreover, annexin A-I has further medical implications in the treatment of cancer. Annexin A-I can be used as a cell surface protein to mark some forms of tumors that can be targeted by various immunotherapies with antibodies against annexin A-I.

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  • 13. 

    Which of the following actions most likely contributes to the immunosuppressive effect of glucocorticoids ?

    • A. 

      Increased plasma levels of free fatty acids

    • B. 

      Increased gluconeogenesis

    • C. 

      Reduced production of TNF in macrophages

    • D. 

      Increased protein synthesis in the liver

    • E. 

      Decreased calcium absorption from the intestine

    Correct Answer
    C. Reduced production of TNF in macrophages
    Explanation
    Glucocorticoids have immunosuppressive effects by reducing inflammation and suppressing the immune response. TNF (tumor necrosis factor) is a pro-inflammatory cytokine produced by macrophages. By reducing the production of TNF in macrophages, glucocorticoids decrease the inflammatory response and contribute to their immunosuppressive effect. This action helps to dampen the immune system and reduce inflammation in various conditions such as autoimmune diseases and organ transplant rejection.

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  • 14. 

    Which of the following statements regarding the pharmacokinetics of corticosteroids are correct? (Check all that apply)

    • A. 

      Oral bioavailability is generally very good

    • B. 

      Substantial absorption does occur through the skin

    • C. 

      They distribute into peripheral tissues but cross the blood-brain barrier with difficulty

    • D. 

      Their biological half-lives can be long (up to 72 hours)

    • E. 

      They are mainly excreted unchanged by the kidney

    Correct Answer(s)
    A. Oral bioavailability is generally very good
    B. Substantial absorption does occur through the skin
    D. Their biological half-lives can be long (up to 72 hours)
    Explanation
    The correct answer is that oral bioavailability is generally very good, substantial absorption does occur through the skin, and their biological half-lives can be long (up to 72 hours). Corticosteroids are well-absorbed when taken orally, and they can also be absorbed through the skin when applied topically. Their long half-lives mean that they stay in the body for an extended period of time before being eliminated. However, they do not distribute easily into the brain due to the blood-brain barrier, and they are not mainly excreted unchanged by the kidney.

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  • 15. 

    Which of the following are effects of glucocorticoids upon carbohydrate metabolism? (Check all that apply)

    • A. 

      Decreased gluconeogenesis in liver

    • B. 

      Increased glucose uptake by skeletal muscle

    • C. 

      Increased glycogen synthesis in liver

    • D. 

      Decreased glucose uptake by adipose tissue

    • E. 

      Increased glucose utilization in peripheral tissues

    Correct Answer(s)
    C. Increased glycogen synthesis in liver
    D. Decreased glucose uptake by adipose tissue
    Explanation
    Glucocorticoids have several effects on carbohydrate metabolism. One of these effects is increased glycogen synthesis in the liver, which means that more glucose is converted into glycogen and stored in the liver. Another effect is decreased glucose uptake by adipose tissue, meaning that adipose tissue takes up less glucose from the blood. These effects help to regulate blood glucose levels and ensure that glucose is available for other tissues that require it, such as skeletal muscle.

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  • 16. 

    A 55-year-old man with Addison’s disease presented to the hospital complaining of episodic weakness, paresthesias, and constipation. He had been taking cortisol and fludrocortisone for several months. On admission his blood pressure was 160/98 mm Hg and an ECG showed prolongation of Q-T interval. Lab results revealed a plasma K+ level of 2.5 mEq/L. Which of the following events best explains the patient syndrome?

    • A. 

      Cortisol induced hyperglycemia

    • B. 

      Fludrocortisone excess

    • C. 

      Inadequate therapy of adrenal insufficiency

    • D. 

      Cortisol induced myopathy

    • E. 

      Essential hypertension

    Correct Answer
    B. Fludrocortisone excess
    Explanation
    The patient's symptoms, including episodic weakness, paresthesias, constipation, and low plasma K+ level, are consistent with hyperaldosteronism caused by excess fludrocortisone. Fludrocortisone is a synthetic corticosteroid that acts as a mineralocorticoid, increasing sodium reabsorption and potassium excretion in the kidneys. This can lead to hypokalemia, which can cause weakness and paresthesias. Additionally, excess aldosterone can cause hypertension, which is supported by the patient's elevated blood pressure. Cortisol-induced hyperglycemia, inadequate therapy of adrenal insufficiency, cortisol-induced myopathy, and essential hypertension are not the best explanations for the patient's symptoms.

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  • 17. 

    A 42-year-old man presented to the hospital with a complaining of weight gain, mild but continuing facial acne, and decreased muscle strength. On physical examination he was found to be a plethoric, red-faced male with violaceus pigmented striae on a protuberant abdomen and relatively thin extremities. Serum potassium levels on admission were 4.5 mEq/L. A CT scan disclosed an adrenal adenoma in the left adrenal gland and the patient was scheduled for surgery. Which of the following drugs was most likely given during and after surgery to this patient?

    • A. 

      Fludrocortisone

    • B. 

      Spironolactone

    • C. 

      Cortisol

    • D. 

      Aminoglutethimide

    • E. 

      Mifepristone

    • F. 

      Ketoconazole

    Correct Answer
    C. Cortisol
    Explanation
    The patient presented with signs and symptoms consistent with Cushing's syndrome, which is caused by excessive cortisol production. The presence of an adrenal adenoma further supports this diagnosis. Surgery to remove the adenoma would result in a sudden decrease in cortisol levels, which could lead to adrenal insufficiency. Therefore, cortisol would be given during and after surgery to ensure adequate adrenal function and prevent adrenal crisis. Fludrocortisone is a mineralocorticoid and would not address the cortisol deficiency. Spironolactone is an aldosterone antagonist and would not be appropriate in this case. Aminoglutethimide, mifepristone, and ketoconazole are all medications used to inhibit cortisol synthesis and would not be given in this situation.

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  • 18. 

    In pheochromocytoma, 3-methoxy-4-hydroxymandelic acid  is formed enzymatically as a breakdown product of norepinephrine. The formation of this metabolite would be slowed down not only by inhibitors of MAO or COMT, but also by a:

    • A. 

      Glutamate decarboxylase inhibitor

    • B. 

      COX-2 inhibitor

    • C. 

      Tricyclic antidepressant

    • D. 

      Tryptophan hydroxylase inhibitor

    • E. 

      Tyrosine hydroxylase inhibitor

    Correct Answer
    E. Tyrosine hydroxylase inhibitor
    Explanation
    A tyrosine hydroxylase inhibitor would slow down the formation of 3-methoxy-4-hydroxymandelic acid because tyrosine hydroxylase is the enzyme responsible for converting tyrosine into norepinephrine. If tyrosine hydroxylase is inhibited, there would be less norepinephrine available for breakdown, leading to a decrease in the formation of 3-methoxy-4-hydroxymandelic acid.

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  • 19. 

    Of these drugs, the one best suited for the treatment of pheochromocytoma is a

    • A. 

      Glutamate decarboxylase inhibitor

    • B. 

      COX-2 inhibitor

    • C. 

      Tricyclic antidepressant

    • D. 

      Tryptophan hydroxylase inhibitor

    • E. 

      Tyrosine hydroxylase inhibitor

    Correct Answer
    E. Tyrosine hydroxylase inhibitor
    Explanation
    A pheochromocytoma is a tumor that originates from the adrenal glands and produces excessive amounts of catecholamines, such as adrenaline and noradrenaline. These hormones are synthesized from the amino acid tyrosine. By inhibiting the enzyme tyrosine hydroxylase, which is responsible for the conversion of tyrosine to dopamine (a precursor for catecholamines), the production of excessive catecholamines can be reduced. Therefore, a tyrosine hydroxylase inhibitor would be the most suitable drug for the treatment of pheochromocytoma.

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  • 20. 

    65 year old man presents with bone pain and is found to have increased parathyroid hormone. A SPECT scan finds all four of the parathyroid glands enlarged. Serum calcium is high and phosphate is low. Serum creatinine is normal. Which of the following is the most probable cause of this patient’s illness?

    • A. 

      Parathyroid adenoma

    • B. 

      Chronic renal failure

    • C. 

      Parathyroid carcinoma

    • D. 

      Primary hyperplasia

    • E. 

      Lung carcinoma

    Correct Answer
    D. Primary hyperplasia
    Explanation
    The most probable cause of this patient's illness is primary hyperplasia. Primary hyperplasia is a condition in which all four parathyroid glands become enlarged and overactive, leading to increased levels of parathyroid hormone. This results in high serum calcium levels and low phosphate levels. The fact that the patient's serum creatinine is normal suggests that renal failure is not the cause of the elevated parathyroid hormone. Parathyroid adenoma and parathyroid carcinoma would typically only involve one gland, rather than all four. Lung carcinoma would not directly cause these symptoms. Therefore, primary hyperplasia is the most likely explanation.

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  • 21. 

    Thyroid hormone (T3 or T4) receptors:

    • A. 

      Bind T3 or T4 in the blood plasma, but do not enter cells.

    • B. 

      Facilitate the entry of T3 or T4 in the cell.

    • C. 

      Are integral membrane proteins that bind T3 or T4 on their extracellular domains.

    • D. 

      Bind T3 or T4 with their leucine zipper domain.

    • E. 

      Bind T3 or T4 with their ligand binding domain and function in the nucleus.

    Correct Answer
    E. Bind T3 or T4 with their ligand binding domain and function in the nucleus.
    Explanation
    Thyroid hormone receptors are integral membrane proteins that bind T3 or T4 on their extracellular domains. They then facilitate the entry of T3 or T4 into the cell. Once inside the cell, the receptors bind T3 or T4 with their ligand binding domain and function in the nucleus. This allows them to regulate gene expression and ultimately impact various physiological processes in the body.

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