Which neurohypophyseal hormone increases water absorption from the kidneys and protects body from dehydration… - RUHS, Jaipur, PB B.Sc Nursing Entrance-2019

RUHS, Jaipur, PB B.Sc Nursing Entrance-2019

Applied Physiology

Easy

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2019

Explanation

Vasopressin, also known as Antidiuretic Hormone (ADH), is synthesized in the hypothalamus and released from the posterior pituitary (neurohypophysis).
Its primary function is to increase water reabsorption in the kidneys' collecting ducts, which concentrates urine and conserves body water.
This action directly protects the body from dehydration by reducing water loss through urine.
The key differentiator is its specific action on renal water permeability, a function not shared by the other listed hormones.

Option B: Oxytocin is also a neurohypophyseal hormone, but its primary roles are stimulating uterine contractions during childbirth and milk ejection for breastfeeding. It does not primarily regulate water absorption.
Option C: Luteinizing Hormone (LH) is secreted by the anterior pituitary (adenohypophysis), not the posterior pituitary (neurohypophysis). Its function is related to reproduction (triggering ovulation in females and testosterone production in males).
Option D: Thyroid Stimulating Hormone (TSH) is also secreted by the anterior pituitary. Its function is to stimulate the thyroid gland to produce thyroid hormones (T3 and T4), which regulate metabolism.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Function of Neurohypophyseal Hormones as background academic context rather than a clinical decision trigger.
A nurse must be able to recognize signs of ADH imbalance. For instance, a patient with Diabetes Insipidus will have polyuria (excessive urination) and polydipsia (excessive thirst), requiring careful fluid management and hormone replacement (e.g., desmopressin).
Conversely, a patient with SIADH will have fluid retention and low sodium levels (hyponatremia), which can lead to confusion, seizures, and coma. Nursing care involves fluid restriction, monitoring neurological status, and administering medications like hypertonic saline.
What if? If a patient on lithium therapy develops polyuria and polydipsia, the nurse should suspect drug-induced nephrogenic diabetes insipidus, where the kidneys become resistant to ADH. The treatment would focus on discontinuing the offending drug if possible, rather than replacing ADH.

How to Approach the Question

First, break down the question's key term: 'neurohypophyseal hormone'. This immediately tells you the hormone must come from the posterior pituitary gland.
Next, identify the main function described: 'increases water absorption from the kidneys' and 'protects body from dehydration'.
Evaluate the options. Eliminate hormones not from the posterior pituitary. Both Luteinizing Hormone and Thyroid Stimulating Hormone are from the anterior pituitary.
This leaves two options from the posterior pituitary: Vasopressin and Oxytocin.
Recall the specific functions of these two hormones. Vasopressin's alternative name is Antidiuretic Hormone (ADH), which literally means it opposes diuresis (water loss). This matches the question's description.
Confirm that Oxytocin's primary roles (uterine contraction, milk ejection) do not match the function described in the question, making Vasopressin the correct choice.

Concept Tested & Keywords

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E6 Medicine Harrison 22e Part 2 p. 919-921

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 2 — Subpart B (pp 240-463 of 478) p. 141-143

E6 Pharmacology Nursing Lilley 11e Part 2 p. 178-180