The hormones that coordinate the storage, absorption, and excretion of calcium ions are (a) growth hormone and thyroxine, (b) calcitonin and parathyroid hormone, (c) calcitriol and cholecalciferol, (d) estrogens and androgens.

Verified step by step guidance

1. Identify the primary function of each hormone listed in the options to determine their role in calcium ion regulation.
2. Understand that calcitonin, produced by the thyroid gland, helps lower blood calcium levels by inhibiting osteoclast activity, which breaks down bone.
3. Recognize that parathyroid hormone, produced by the parathyroid glands, increases blood calcium levels by stimulating osteoclasts to break down bone and release calcium.
4. Analyze the roles of other hormones listed in the options to see if they directly influence calcium ion storage, absorption, or excretion.
5. Conclude which pair of hormones directly coordinates the processes of calcium ion storage, absorption, and excretion in the body.

Key Concepts

Calcitonin

Calcitonin is a hormone produced by the thyroid gland that helps regulate calcium levels in the blood. It lowers blood calcium levels by inhibiting osteoclast activity, which decreases bone resorption, and promoting calcium excretion by the kidneys. This hormone plays a crucial role in maintaining calcium homeostasis, especially after meals when calcium levels may rise.

Parathyroid Hormone (PTH)

Parathyroid hormone is secreted by the parathyroid glands and is essential for increasing blood calcium levels. It stimulates osteoclasts to break down bone and release calcium, enhances calcium reabsorption in the kidneys, and promotes the activation of vitamin D, which increases intestinal absorption of calcium. PTH and calcitonin work in opposition to maintain calcium balance.

Calcium Homeostasis

Calcium homeostasis refers to the regulation of calcium levels in the body, which is vital for various physiological functions, including muscle contraction, nerve transmission, and blood clotting. The balance between calcium intake, storage in bones, and excretion is maintained by hormones like calcitonin and parathyroid hormone, ensuring that calcium levels remain within a narrow range for optimal health.