Calcitonin hormone is secreted by -

Appeared in: UPPSC 2023

Explanation

Calcitonin is a hormone produced by the parafollicular cells, also known as C-cells, which are located in the thyroid gland.
The primary function of calcitonin is to regulate calcium and phosphate levels in the blood, specifically by lowering high blood calcium levels (hypercalcemia).
It achieves this by inhibiting the activity of osteoclasts (cells that break down bone tissue) and increasing the excretion of calcium by the kidneys.

Option A: Mast cells are components of the immune system, primarily involved in allergic reactions and inflammation through the release of substances like histamine and heparin.
Option B: Follicular cells are the most abundant cell type in the thyroid gland, but they are responsible for synthesizing and secreting the thyroid hormones T3 (triiodothyronine) and T4 (thyroxine), which control metabolism.
Option D: Macrophages are phagocytic white blood cells that are a crucial part of the innate immune system. Their main role is to engulf and digest cellular debris, foreign substances, and microbes.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Source of Calcitonin hormone secretion as background academic context rather than a clinical decision trigger.
Blood levels of calcitonin are used as a crucial tumor marker for diagnosing and monitoring Medullary Thyroid Carcinoma (MTC), a cancer originating from the parafollicular cells.
Synthetic calcitonin (e.g., from salmon) is used therapeutically to treat conditions like postmenopausal osteoporosis, Paget's disease of bone, and severe hypercalcemia, as it helps reduce bone resorption and lower blood calcium.
What if the question asked which hormone raises blood calcium levels? The answer would be Parathyroid Hormone (PTH), which is secreted by the parathyroid glands and has effects largely opposite to those of calcitonin.

How to Approach the Question

This is a factual recall question testing knowledge of the endocrine system.
First, identify the key substance in the question: the hormone Calcitonin.
Next, recall the major endocrine glands and the hormones they produce.
Associate Calcitonin with the thyroid gland.
Differentiate between the two main hormone-producing cell types within the thyroid: follicular cells (which make T3/T4 for metabolism) and parafollicular cells (which make calcitonin for calcium regulation).
Evaluate the given options. Mast cells and macrophages are immune cells, not endocrine cells for calcium control. Follicular cells produce different hormones. This process of elimination confirms that parafollicular cells are the correct answer.

Concept Tested & Keywords

QjD9R5kpErjc4N-15ncgYl

E6 Pharmacology KD Tripathi Essentials 9e Part 2 p. 12-14

E6 Anatomy Grays 43e Vol 2 Part 1 p. 45-47

E6 Nursing Brunner Adult Health 3SA Vol 1 Part 4 p. 12-14

Practise the full UPPSC 2023

Attempt every question from this paper in a timed mock, then review the full solution for each one.