The hormone that helps in maintaining fluid balance is?

VSSC Nursing Officer - 2021

Applied Physiology

Easy

Appeared in: VSSC Nursing Officer - 2021

Explanation

Antidiuretic Hormone (ADH), also known as vasopressin, is the primary hormone that regulates the body's water balance.
It is synthesized in the hypothalamus and released from the posterior pituitary gland in response to increased plasma osmolarity or decreased blood volume.
ADH acts on the distal convoluted tubules and collecting ducts of the kidneys, increasing their permeability to water.
This enhances water reabsorption from the filtrate back into the blood, thereby reducing urine output and conserving body water.

Option A: Prolactin's primary function is to stimulate and maintain milk production (lactation) in the mammary glands after childbirth. It does not play a direct role in regulating the body's overall fluid balance.
Option C: Oxytocin's main roles are stimulating uterine contractions during labor and promoting milk ejection (the 'let-down' reflex) during breastfeeding. While it has a very weak antidiuretic effect, it is not the primary hormone for fluid balance.
Option D: Gonadotropin-releasing hormone (GnRH) is a hypothalamic hormone that controls the reproductive system. It stimulates the anterior pituitary to release Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH), which are essential for ovulation and spermatogenesis.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal regulation of fluid balance as background academic context rather than a clinical decision trigger.
Understanding ADH is crucial for managing fluid and electrolyte imbalances. A deficiency of ADH causes Diabetes Insipidus, characterized by severe dehydration and electrolyte disturbances if not managed.
Conversely, excess ADH (SIADH) leads to water intoxication and hyponatremia, which can cause cerebral edema and neurological symptoms. Nurses must monitor fluid intake, output, urine specific gravity, and serum sodium levels in these patients.
What if? If a patient has a head injury affecting the hypothalamus or pituitary gland, the nurse must be vigilant for signs of either ADH deficiency (polyuria) or excess (oliguria and fluid retention), as both are potential complications.

How to Approach the Question

First, identify the key concept in the question stem, which is 'maintaining fluid balance'.
Next, analyze the term 'Antidiuretic Hormone' (ADH). 'Anti-' means against, and 'diuresis' means increased urine production. Therefore, the hormone's function is to work against urine production, thus conserving water.
Systematically review the primary function of each hormone listed in the options.
Compare the function of each hormone to the requirement of the question ('fluid balance').
Eliminate the options whose primary functions are related to reproduction (GnRH, Prolactin) or childbirth/lactation (Oxytocin).
Conclude that ADH is the only hormone listed whose primary role is the direct regulation of water retention by the kidneys.

Concept Tested & Keywords

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

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