Block 5 Endo Hormone Synth MCQ's
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- 1.
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.
T4reduced, TSH normal
Correct Answer
D. T4 reduced, TSH elevatedExplanation
If a patient presents with signs of hypothyroidism and has iodine deficiency, it can be expected that the levels of T4 (thyroxine) will be reduced and the levels of TSH (thyroid-stimulating hormone) will be elevated. This is because iodine is necessary for the production of thyroid hormones, including T4. In the presence of iodine deficiency, the thyroid gland is unable to produce sufficient amounts of T4, leading to a decrease in T4 levels. In response, the pituitary gland releases more TSH to stimulate the thyroid gland to produce more thyroid hormones, resulting in elevated TSH levels.Rate this question:
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- 2.
This structure is:
- A.
An estrogen
- B.
An androgen
- C.
A glucocorticoid
- D.
A mineralocorticoid
- E.
Progesterone
Correct Answer
D. A mineralocorticoidExplanation
A mineralocorticoid is a type of steroid hormone that regulates electrolyte and water balance in the body. It acts on the kidneys to increase the reabsorption of sodium and the excretion of potassium, helping to maintain proper fluid balance. Estrogen, androgen, glucocorticoid, and progesterone are all different types of hormones with different functions, but they do not specifically regulate electrolyte and water balance like a mineralocorticoid does.Rate this question:
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- 3.
An elderly patient who takes aspirin for chronic arthritis complains about frequent pain in the stomach that can be relieved only by eating. One possible solution to the patient's problem is to
- A.
Raise the aspirin dose to reduce the stomach pain
- B.
Switch to a drug that has higher potency on COX-1relative to COX-2
- C.
Switch to a drug that has higher potency on COX-2 relative to COX-1
- D.
Use a selective inhibitor of prostaglandin E synthesis
- E.
Use aspirin in combination with a converting enzyme inhibitor
Correct Answer
C. Switch to a drug that has higher potency on COX-2 relative to COX-1Explanation
The patient is experiencing stomach pain, which is a common side effect of aspirin use. Aspirin inhibits both COX-1 and COX-2 enzymes, which are involved in the production of prostaglandins. Prostaglandins play a protective role in the stomach lining, so inhibiting their production can lead to stomach irritation and pain. Switching to a drug that has higher potency on COX-2 relative to COX-1 would help to reduce stomach irritation and pain while still providing relief for chronic arthritis.Rate this question:
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- 4.
During the synthesis of steroid hormones, side chain cleavage reactions occur in two biotransformations. These are:
- A.
Glucocorticoids ---> mineralocorticoids and progestins --> androgens
- B.
Progestins --> corticosteroids and androgens --> estrogens
- C.
Cholesterol --> progestins and estrogens --> androgens
- D.
Cholesterol --> progestins and progestins --> androgens
- E.
Androgens --> corticosteroids and androgens--> estrogens
Correct Answer
D. Cholesterol --> progestins and progestins --> androgensExplanation
During the synthesis of steroid hormones, side chain cleavage reactions occur in two biotransformations. Cholesterol is converted into progestins, which are then further converted into androgens. This is the correct answer because it accurately describes the sequence of reactions in the synthesis of steroid hormones.Rate this question:
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- 5.
Thromboxane is formed in platelets, where it promotes platelet activation. The formation of thromboxane can be suppressed by inhibitors of:
- A.
2l-hydroxylase
- B.
COX-2
- C.
5-lipoxygenase
- D.
Desmolase
- E.
COX-I
Correct Answer
E. COX-IExplanation
Thromboxane is formed in platelets through the action of cyclooxygenase-1 (COX-I). COX-I is an enzyme responsible for the synthesis of prostaglandins and thromboxane, which promote platelet activation and aggregation. Inhibitors of COX-I, such as aspirin, can suppress the formation of thromboxane and inhibit platelet activation. Therefore, COX-I inhibitors can be used to prevent excessive platelet activation and reduce the risk of blood clot formation.Rate this question:
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- 6.
For a “classical" radioimmunoassay of insulin, you need
- A.
Radiolabeled insulin receptor
- B.
Radioactive insulin in the test tube
- C.
Injection of radioactive insulin in the patient
- D.
A radioactive antibody
- E.
Two-dimensional electrophoresis
Correct Answer
B. Radioactive insulin in the test tubeExplanation
In a "classical" radioimmunoassay of insulin, radioactive insulin is needed in the test tube. This is because the radioimmunoassay relies on the binding of insulin to its receptor. By using radioactive insulin, the binding can be easily detected and measured. The test tube serves as the environment where the binding reaction takes place, allowing for the quantification of insulin levels in the sample being tested. The other options, such as a radiolabeled insulin receptor, injection of radioactive insulin, a radioactive antibody, and two-dimensional electrophoresis, are not necessary for the classical radioimmunoassay of insulin.Rate this question:
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- 7.
The antihypertensive drug captopril acts as an inhibitor of angiotensin converting enzyme. In addition to reducing the formation of angiotensin II, captopril will also reduce the level of circulating
- A.
Cortisol
- B.
Bradykinin
- C.
Thromboxane
- D.
Aldosterone
- E.
Insulin
Correct Answer
D. AldosteroneExplanation
Captopril inhibits angiotensin converting enzyme (ACE), which is responsible for converting angiotensin I to angiotensin II. Angiotensin II stimulates the release of aldosterone from the adrenal glands. Therefore, by reducing the formation of angiotensin II, captopril will also reduce the level of circulating aldosterone.Rate this question:
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- 8.
The nurse notices that a newborn girl has an unusually enlarged clitoris, and asks you whether this might be a disorder of sexual development. You notice that in addition to the large clitoris the labia are partially fused. Some tests are done. The hospital lab reports normal values for serum sodium, potassium and ACTH. An ultrasound scan shows normal sized adrenal glands. A buccal smear is sex chromatin negative (no Barr body). If this child has an enzyme deficiency, the missing enzyme is most Iikely
- A.
Desmolase
- B.
21-hydroxylase
- C.
11-hydroxylase
- D.
Aromatase
- E.
5a-reductase
Correct Answer
E. 5a-reductaseExplanation
The correct answer is 5a-reductase. This is because the newborn girl has an enlarged clitoris and partially fused labia, which are characteristic features of a disorder of sexual development called congenital adrenal hyperplasia (CAH). CAH is most commonly caused by a deficiency in the enzyme 21-hydroxylase, which leads to an increase in androgen production. However, in this case, the lab tests show normal values for serum sodium, potassium, and ACTH, indicating that the adrenal glands are functioning normally. Additionally, the buccal smear is sex chromatin negative, ruling out any chromosomal abnormalities. Therefore, the most likely cause of the newborn's symptoms is a deficiency in 5a-reductase, an enzyme responsible for converting testosterone to dihydrotestosterone (DHT), which is important for the development of male external genitalia.Rate this question:
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- 9.
After several attacks of autoimmune thyroiditis, Mrs. O. has developed signs of hypothyroidism. Her hormone measurements will most likely show:
- A.
HighT4, high TSH
- B.
HighT4, low TSH
- C.
Low T4, low TSH
- D.
Low T4, high TSH
- E.
Low T4, normal TSH
Correct Answer
D. Low T4, high TSHExplanation
After several attacks of autoimmune thyroiditis, Mrs. O. has developed signs of hypothyroidism. In hypothyroidism, the thyroid gland does not produce enough thyroid hormones, resulting in low levels of T4. As a compensatory mechanism, the pituitary gland releases more TSH (thyroid-stimulating hormone) to stimulate the thyroid gland to produce more hormones. Therefore, the hormone measurements in Mrs. O. will most likely show low T4 levels and high TSH levels.Rate this question:
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- 10.
The hydroxylation reactions of steroid hormones in the endocrine glands require cytochromeP450, NADPH and
- A.
Tetrahydrobiopterin
- B.
Pyridoxal phosphate(vitamin B6)
- C.
S-adenosyl-methionine
- D.
Molecular oxygen
- E.
Biotin
Correct Answer
D. Molecular oxygenExplanation
The hydroxylation reactions of steroid hormones in the endocrine glands require molecular oxygen. Oxygen is necessary for the hydroxylation process, which involves adding a hydroxyl group (-OH) to the steroid molecule. This reaction is catalyzed by cytochrome P450 enzymes, which use molecular oxygen as a co-substrate. Without oxygen, the hydroxylation reactions cannot occur, leading to a disruption in the synthesis of steroid hormones.Rate this question:
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- 11.
Insulin is synthesized from a larger precursor protein. The following events occur during insulin synthesis: (1) Formation of disulfide bonds; (2) Secretion by exocytosis; (3) Removal of the signal sequence (4) Removal of the C-peptide, In which sequence are these events most likely to occur?
- A.
1--> 3 -->4 --> 2
- B.
3 --> 2--> 1--> 4
- C.
3 --> 1 --> 4 --> 2
- D.
4 --> 3 --> 2 -->1
- E.
4 --> 3 --> 1 --> 2
Correct Answer
C. 3 --> 1 --> 4 --> 2Explanation
During insulin synthesis, the signal sequence is first removed, allowing the protein to move to the endoplasmic reticulum. Then, disulfide bonds are formed, stabilizing the protein structure. Next, the C-peptide is removed, leaving only the mature insulin molecule. Finally, the mature insulin is secreted by exocytosis. Therefore, the most likely sequence of events is 3 --> 1 --> 4 --> 2.Rate this question:
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- 12.
Selective COX-2 inhibitors have been developed, but they should be used with caution because they can increase the risk of
- A.
Venous thrombosis
- B.
Psychosis
- C.
Gastric ulcer
- D.
Acute myocardial infarction
- E.
Inflammation
Correct Answer
D. Acute myocardial infarctionExplanation
Selective COX-2 inhibitors are a type of medication that are used to reduce inflammation and pain. However, they have been found to increase the risk of acute myocardial infarction, also known as a heart attack. This is because COX-2 inhibitors can interfere with the normal functioning of blood vessels, leading to the formation of blood clots and potentially blocking blood flow to the heart. Therefore, caution should be exercised when using these medications, especially in individuals who are already at a higher risk of heart disease.Rate this question:
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- 13.
Low doses of aspirin are used to reduce the risk of acute myocardial infarction. Which enzyme is targeted when aspirin is used for this purpose?
- A.
5-lipoxygenase
- B.
12-lipoxygenase
- C.
COX-1
- D.
COX-2
- E.
COX-3
Correct Answer
C. COX-1Explanation
Aspirin is used to reduce the risk of acute myocardial infarction by targeting the enzyme COX-1. COX-1 is responsible for the production of thromboxane A2, a substance that promotes platelet aggregation and blood clot formation. By inhibiting COX-1, aspirin prevents the formation of thromboxane A2, reducing the risk of blood clots and subsequent heart attacks.Rate this question:
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Mar 21, 2023Quiz Edited by
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Feb 14, 2012Quiz Created by
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