This set of Molecular Endocrinology Multiple Choice Questions & Answers (MCQs) focuses on “Posterior Pituitary – Diabetes Insipidus – Set 2”.
1. The syndrome of transient hyponatremia has been referred to as?
a) Isolated second phase
b) Acquired second phase
c) Inhibitory second phase
d) Mutant second phase
View Answer
Explanation: Isolated second phase is the synonym used to refer the syndrome of transient hyponatremia. This condition occurs in cases where there is electrolyte imbalance like sodium deficiency. Isolated second phase mainly happens to persons with congenital heart diseases, kidney failure, liver failure etc.
2. What does the lack of thirst in response to increased osmolality indicates?
a) Abnormality of the pressure
b) Abnormality of the osmostat
c) Abnormality in ADH secretion
d) Abnormality in Oxytocin secretion
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Explanation: An osmostat abnormality is suggested by lack of thirst in response to increased osmolality. In neurohypophysial DI, this can be seen if the original lesion or surgical damage is so severe that it affects not only the neurohypophysis but also the central anterior osmostat, or if the osmostat is isolated with intact baroreceptors.
3. Abnormalities of thirst with primary hypothalamic lesions are most common in patients with which among the following conditions?
a) Craniopharyngioma
b) Adenohypophysis
c) Sarcoidosis
d) Lymphosis
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Explanation: Thirst defects of primary hypothalamic lesions are most prominent in sarcoidosis patients. However, after the clipping of an anterior communicating artery aneurysm, the pattern of critical hypernatremia with absent osmostat and intact baroreceptor is most widely recorded.
4. Second phase of the triphasic response may occur without preceding or subsequent DI.
a) True
b) False
View Answer
Explanation: A significant finding is that there could be a second stage of triphasic reaction (i.e., uncontrolled release of vasopressin due to axon trauma) without preceding or subsequent DI. This was clinically recorded and developed by unilateral lesion of the supraoptic hypophysial track.
5. Cortisol deficiency should also be considered subsequently if DI appears to “improve”.
a) True
b) False
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Explanation: Subsequently, cortisol deficiency should also be considered if DI tends to “improve” in the absence of an administered antidiuretic agent due to reduced water excretion. Lastly, partial DI can be observed in the long-term follow-up of these patients.
6. Which among the following is an example of Natriuretic agent used in the treatment of Diabetes Insipidus?
a) L-Arginine vasopressin
b) Amiloride
c) Chlorpropamide
d) Carbamazepine
View Answer
Explanation: Amiloride is an example of Natriuretic agent used in the treatment of Diabetes Insipidus. A major objective of therapy is to reduce thirst and polyuria to a degree that enables a normal lifestyle to be sustained by the patient.
7. Why Water is considered a therapeutic agent for the treatment of DI?
a) No metabolic abnormality if taken sufficiently
b) Induce metabolic changes
c) Increases polyuria if taken sufficiently
d) Increases adenohypophysis if taken sufficiently
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Explanation: Water is considered a therapeutic agent since there is no metabolic abnormality if it is taken in adequate amounts. As noted, therapy is designed to reduce to an appropriate level of the required water intake (and polyuria).
8. In desmopressin, the substitution of which amino acid markedly reduces pressor activity?
a) D-cysteine
b) L-cysteine
c) L-arginine
d) D-arginine
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Explanation: The medication of choice for DI is desmopressin, a synthetic vasopressin analogue in which D-arginine replacement greatly decreases pressure activity and increases the half-life by eliminating the terminal amine. The two modifications create an antidiuresis agent approximately 2000 times more specific than L-arginine vasopressin, which occurs naturally.
9. Which among the following drugs are useful for cases in which only a modest decrease in urine volume will make the patient asymptomatic?
a) Chlorpropamide
b) Allopurinol
c) Zyloprim
d) Zintec
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Explanation: Therapeutic agents such as chlorpropamide or thiazide diuretics are particularly beneficial in cases where the patient becomes asymptomatic only because of a small drop in urine volume. The action on the renal tubule by chlorpropamide is to improve the hydro osmotic activity of residual vasopressin.
10. Why Chlorpropamide should not be used in pregnancy and is not recommended for children?
a) There is possibility of severe hyperglycemia
b) There is possibility of severe hypoglycemia
c) There is possibility of severe antidiuresis
d) There is possibility of severe adenohypophysis
View Answer
Explanation: Chlorpropamide is not recommended for use during pregnancy and is not recommended for children, especially those suffering from concomitant hypopituitarism. This is because of the risk of extreme hypoglycemia.
11. Which among the following is a rare complication of desmopressin therapy?
a) Hyponatremia
b) Hypoglycemia
c) Hypothyroidism
d) Hyperthyroidism
View Answer
Explanation: Hyponatremia is a rare complication of therapy with desmopressin which occurs only if the patient is consistently antidiuretic while retaining adequate fluid intake to expand the natriuretic volume. Thirst may be defensive, and most patients are not consistently maximally antidiuretic on regular therapy or may postpone a dose periodically to excrete any excess retained water.
12. Which among the following enzymes causes the two types of transient DI during pregnancy?
a) Cysteine aminopeptidase
b) Lysine aminopeptidase
c) Arginine aminopeptidase
d) Leucine aminopeptidase
View Answer
Explanation: In pregnancy, there are two types of transient DI, both induced by the cysteine aminopeptidase (oxytocinase) enzyme. Oxytocinase is a type of enzyme that metabolizes oxytocin, which is an endogenous neuropeptide.
13. What is the type of the transient DI seen in pregnant women, where, the activity of Cysteine aminopeptidase is extremely and abnormally elevated?
a) Vasopressin-resistant DI of pregnancy
b) Oxytocin-resistant DI of pregnancy
c) Estrogen- resistant DI of pregnancy
d) Progesterone-resistant DI of pregnancy
View Answer
Explanation: The activity of the Cysteine aminopeptidase enzyme (which is also a vasopressinase) is highly and abnormally elevated in the first form of transient DI in pregnant women. This condition has been referred to in pregnancy as vasopressin-resistant DI.
14. Which is the only therapy recommended for treatment of DI during pregnancy?
a) Desmopressin
b) Chlorpropamide
c) Amiloride
d) Allopurinol
View Answer
Explanation: The only medication prescribed for treatment of DI during pregnancy is desmopressin. Desmopressin has the oxytocic effect of lysine vasopressin or arginine vasopressin at 2 to 25 percent and can be used with limited oxytocin receptor stimulation in the uterus.
15. Which among the following is one of the two causes of nephrogenic DI?
a) Mutation in the V2 receptor
b) Mutation in the V1 receptor
c) Mutations of the aquaporin 4 water channels
d) Mutations in the Ig receptor
View Answer
Explanation: Two causes of nephrogenic DI are present: V2 receptor mutation and aquaporin 2 water channel mutations. The presentation is genotype independent. More than 90% of nephrogenic DI cases are X-linked recessive disorders in males with more than 200 distinct V2 receptor mutations.
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