Endocrinology Practice Questions

Q: Which of the following is NOT true about vasopressin?

It is structurally similar to insulin. ***It is structurally similar to insulin*** - **Vasopressin** (arginine vasopressin or ADH) is a **nonapeptide** (9 amino acids), whereas **insulin** is a larger protein composed of 51 amino acids in two chains. Their structures are distinct and not similar. - While both are peptide hormones, their primary amino acid sequences and overall three-dimensional structures differ significantly, leading to distinct receptor interactions and physiological roles. *It increases peripheral vascular resistance* - Vasopressin acts on **V1 receptors** located on vascular smooth muscle, causing **vasoconstriction**. - This vasoconstriction leads to an increase in **peripheral vascular resistance** and, consequently, an elevation in **blood pressure**. *It is released in response to increased plasma osmolality* - **Osmoreceptors** in the hypothalamus detect increased **plasma osmolality** (due to dehydration or high solute concentration). - This triggers the release of vasopressin from the **posterior pituitary**, promoting water reabsorption to dilute the plasma. *It acts on V2 receptors in renal collecting ducts* - Vasopressin binds to **V2 receptors** on the basolateral membrane of principal cells in the **renal collecting ducts**. - This binding leads to the insertion of **aquaporin-2 channels** into the apical membrane, increasing water permeability and reabsorption.

Question 1

Which of the following is NOT true about vasopressin?

Accepted Answer

It is structurally similar to insulin

Answer

It is released in response to increased plasma osmolality

Answer

It increases peripheral vascular resistance

Answer

It acts on V2 receptors in renal collecting ducts

Question 2

Disruption of the hypothalamic-pituitary portal system will lead to

Accepted Answer

High circulating levels of PRL, low levels of LH and FSH, leading to ovarian atrophy.

Answer

Increased follicular development due to elevated circulating levels of PRL.

Answer

Ovulation with subsequent increase in circulating progesterone levels.

Answer

Increased FSH levels due to reduced ovarian inhibin levels.

Endocrinology — MCQs

Endocrinology — MCQs

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