How Do the Hormones Involved in Blood Calcium Homeostasis Actually

Question

How do the hormones involved in blood calcium homeostasis actually function?
A) Parathyroid hormone stimulates calcium deposit in bones and increases calcium uptake in the kidneys.
B) A falling blood calcium level causes the thyroid to release calcitonin.
C) Calcitonin acts to lower blood calcium levels, and parathyroid hormone acts to raise blood calcium.
D) Both parathyroid hormone and calcitonin act to raise blood calcium levels.

Accepted Answer

Calcitonin acts to decrease blood calcium levels, while parathyroid hormone acts to increase blood calcium levels. This helps maintain blood calcium homeostasis. A falling blood calcium level can stimulate the parathyroid gland to release parathyroid hormone, while a rise in blood calcium can stimulate the thyroid gland to release calcitonin. Parathyroid hormone stimulates calcium release from bones, increases calcium reabsorption in the kidneys, and activates vitamin D, which in turn enhances calcium absorption in the small intestine. Calcitonin inhibits calcium release from bones and decreases calcium reabsorption in the kidneys.