Problem 4 - Biology of Humans: Concepts, Applications, and Issues

Question

Which of the following hormones raises the blood level of calcium? a. calcitonin b. estrogen c. parathyroid hormone d. all of the above

Step-by-Step Solution

Answer

c. parathyroid hormone

Step 1: Understand the Hormones Involved

First, it's important to understand the roles of calcitonin, estrogen, and parathyroid hormone in calcium regulation. Calcitonin lowers the blood level of calcium. Estrogen does not primarily regulate calcium directly, but rather has roles in reproductive and secondary sexual characteristics. Parathyroid hormone raises the blood level of calcium.

Step 2: Identify the Correct Answer

Given the information about each hormone's function, it is clear that parathyroid hormone (option c) is the one that raises the blood level of calcium.

Step 3: Confirm the Answer

Re-examine the question and the roles of the hormones to ensure the answer is correct. Calcitonin and estrogen do not raise calcium levels in the blood, only parathyroid hormone does.

Key Concepts

calcitonin function

Calcitonin is a hormone produced by the thyroid gland. It plays a crucial role in regulating calcium levels in the blood. When calcium levels are high, calcitonin is secreted to lower these levels. It does this by:
- Inhibiting the activity of osteoclasts, which are cells that break down bone tissue and release calcium into the bloodstream
- Increasing the amount of calcium excreted in the urine
By performing these functions, calcitonin helps maintain calcium balance in the body and supports bone health.

estrogen role

Estrogen is primarily known for its role in the development of female reproductive tissues and secondary sexual characteristics. However, it also influences bone density and calcium balance. Although estrogen does not directly regulate calcium levels in the blood, it plays an indirect role by:
- Promoting the activity of osteoblasts, which are cells that form new bone
- Reducing bone resorption, which helps in maintaining bone density
Therefore, while estrogen is not primarily responsible for regulating blood calcium levels, it does contribute to overall bone health and stability.

parathyroid hormone

Parathyroid hormone (PTH) is produced by the parathyroid glands and is crucial for calcium regulation in the body. Unlike calcitonin, PTH raises blood calcium levels when they are too low. It achieves this through several mechanisms:
- Stimulating osteoclasts to break down bone tissue and release calcium into the bloodstream
- Increasing the absorption of calcium in the intestines by promoting the activation of vitamin D
- Reducing the excretion of calcium in the urine
By performing these functions, PTH ensures that calcium levels in the blood remain within a healthy range, thus supporting various physiological processes such as muscle contraction and nerve function.