Parathyroid hormone action is antagonized by?

RUHS, Jaipur, M.Sc Nursing Entrance Exam-2021

Applied Physiology

Easy

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2021

Explanation

Calcitonin is a hormone secreted by the parafollicular cells (C-cells) of the thyroid gland that directly opposes the effects of Parathyroid Hormone (PTH).
PTH works to increase low blood calcium levels, while calcitonin works to decrease high blood calcium levels.
This antagonistic relationship is crucial for maintaining calcium homeostasis, keeping blood calcium within a narrow physiological range.
Calcitonin achieves its effect by inhibiting the activity of osteoclasts (cells that break down bone) and increasing the excretion of calcium by the kidneys.

Option A: Insulin is a pancreatic hormone that regulates blood glucose levels by promoting glucose uptake into cells. It does not have a primary role in calcium regulation.
Option C: Glucagon is a pancreatic hormone that raises blood glucose levels by stimulating glycogenolysis and gluconeogenesis in the liver. It antagonizes insulin, but its primary role is in glucose metabolism, not calcium.
Option D: Oxytocin is released from the posterior pituitary gland and is primarily involved in stimulating uterine contractions during labor and promoting milk ejection (let-down) during lactation. It has no role in blood calcium regulation.

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.
Nurses must understand this hormonal relationship to care for patients with endocrine disorders like hyperparathyroidism (leading to hypercalcemia) or after a thyroidectomy (which carries a risk of hypocalcemia due to inadvertent parathyroid gland damage).
Monitoring serum calcium levels and recognizing signs of imbalance are critical nursing responsibilities. Key signs include tetany and paresthesias in hypocalcemia, and muscle weakness, constipation, and confusion in hypercalcemia.
What if? If a patient has had a total thyroidectomy, they are at risk for both hypothyroidism (lack of thyroid hormone) and hypoparathyroidism (from accidental removal of parathyroid glands). The immediate life-threatening concern is acute hypocalcemia from the lack of PTH, requiring close monitoring for Chvostek's and Trousseau's signs and potential IV calcium administration. The loss of calcitonin is generally not clinically significant.

How to Approach the Question

This is a factual recall question from endocrine physiology.
First, identify the function of the hormone mentioned in the question stem: Parathyroid Hormone (PTH) acts to increase blood calcium levels.
The keyword 'antagonized' means you need to find a hormone that has the opposite effect, i.e., one that decreases blood calcium.
Systematically evaluate each option's primary function:
Insulin: Lowers blood glucose.
Calcitonin: Lowers blood calcium.

Concept Tested & Keywords

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