Parathyroid Hormones and Calcitonin

Where are PTH and calcitonin stored?

PTH is stored in the parathyroid while calcitonin is stored in the thyroid.

What hormones regulate calcium ion level in the blood?

Parathyroid hormones and calcitonin.

What are the roles of PTH and calcitonin?

Parathyroid hormones raise the level of calcium ions in the blood. Calcitonin lowers the level of calcium ions in the blood.

Why is it important to maintain the set level of calcium ions in the blood?

To promote healthy bone growth.

Describe the feedback loop when calcium ion levels fall below the set point.

When calcium ion levels fall below the set point, the parathyroid gland releases PTH, which does three things. PTH causes bones to release calcium ions. PTH causes kidneys reabsorb calcium ions through the renal tubules. The uptake of calcium ions by kidneys from PTH promote the conversion of vitamin D to an active hormone in the liver, causing the kidneys to uptake more calcium ions. These all cause blood calcium ion levels to rise.

What happens when blood calcium ion levels rise or fall from the set point.

When calcium ion levels fall, skeletal muscles begin to contract convulsively (tetany). When calcium ion levels rise, precipitates of calcium phosphate can form in body tissues, leading to widespread organ damage.

Describe the feedback loop when calcium ions rise below the set point.

When calcium ions rise above the set point, the thyroid gland release calcitonin, which does two things. Calcitonin stimulates calcium ion deposition in bones. Calcitonin reduces calcium ion uptake in the kidneys. These both cause blood calcium ion levels to fall.