Question

What is the function of calcitonin?

• A. It increases the calcium level in the blood
• B. It decreases calcium levels in blood
• C. It stimulates steroid synthesis
• D. It increases the absorption of water in kidney tubules

Answer 1

The correct option is B

It decreases calcium levels in blood

The correct option is B.

Explanation of the correct option:

1. Calcitonin hormone is secreted by the C-cells of the thyroid gland.
2. Its main function is to reduce the level of calcium in the blood.
3. Calcium balance is maintained by the action of calcitonin and its antagonist, parathyroid hormone which increases calcium levels.

Explanation of the incorrect options:

Option A:

1. The parathyroid hormone secreted by the parathyroid gland is responsible for increasing calcium levels.
2. If blood calcium levels are low, the PTH is released in the blood increasing the calcium levels.

Option C:

1. The hypothalamus secretes hormones that instruct other organs to produce steroids.
2. For example, the hypothalamic gonadotropin-releasing hormone stimulates the synthesis of luteinizing hormone and follicle-stimulating hormone that in turn stimulate the male and female sex organs to synthesize steroids such as androgens, estrogens, and progesterone.

Option D:

The increased reabsorption of water in the kidney tubules is due to the antidiuretic hormone.

Final Answer: The function of calcitonin is to decrease calcium levels in the blood.