Which hormone acts on the intestines and causes increased calcium absorption?

RUHS, Jaipur, PB B.Sc Nursing Entrance-2020

Applied Physiology

Easy

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2020

Explanation

Calcitriol is the active form of Vitamin D, also known as 1,25-dihydroxycholecalciferol.
It directly targets the epithelial cells of the small intestine to enhance the absorption of dietary calcium.
Its mechanism involves stimulating the genetic transcription of calbindin, a protein that binds to calcium and transports it across the intestinal cell into the blood.
This action makes Calcitriol the principal hormone responsible for increasing blood calcium levels through intestinal absorption.

Option A: Calcitonin's primary function is to lower blood calcium levels, which is the opposite of the action described in the question. It achieves this by inhibiting osteoclast activity, thus reducing bone resorption.
Option C: Thyroxine is a thyroid hormone that primarily regulates the body's basal metabolic rate. It does not have a direct or primary role in the intestinal absorption of calcium.
Option D: Pancreatic polypeptide is involved in the regulation of pancreatic exocrine and endocrine secretions and has effects on satiety and gut motility. It is not involved in calcium homeostasis.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal regulation of calcium homeostasis as background academic context rather than a clinical decision trigger.
Understanding calcium regulation is vital for nurses managing conditions like osteoporosis, hypocalcemia, and chronic kidney disease.
Patients with Vitamin D deficiency cannot produce enough Calcitriol, leading to poor calcium absorption and bone diseases like rickets in children and osteomalacia in adults.
Nurses often educate patients on the importance of adequate sunlight exposure and dietary intake of Vitamin D and calcium for bone health.

How to Approach the Question

First, identify the key concepts in the question: 'hormone,' 'intestines,' and 'increased calcium absorption.' This points to the physiological regulation of minerals.
Second, recall the main hormones involved in calcium balance: Parathyroid Hormone (PTH), Calcitonin, and Calcitriol (the active form of Vitamin D).
Third, differentiate their primary sites of action. Remember that Calcitriol's most prominent role is to act on the gut (intestines). PTH primarily acts on bone and kidneys, and Calcitonin primarily acts on bone.
Fourth, evaluate the options based on this knowledge. Calcitriol is the only hormone listed whose main function is to increase calcium absorption from the intestines.
Eliminate the other options: Calcitonin does the opposite (lowers calcium), and Thyroxine and Pancreatic polypeptide have different primary functions.

Concept Tested & Keywords

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E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 2 — Subpart A (pp 1-239 of 478) pp. 162-164, 163-165

E6 Pharmacology KD Tripathi Essentials 9e Part 2 p. 11-13