Calcitonin

Definition

Calcitonin is a hormone produced by the thyroid gland that helps regulate blood calcium levels. It lowers blood calcium by inhibiting osteoclast activity and promoting calcium excretion in the kidneys.

5 Must Know Facts For Your Next Test

1. Calcitonin is secreted by the parafollicular cells (C-cells) of the thyroid gland.
2. The primary action of calcitonin is to decrease blood calcium levels.
3. Calcitonin inhibits osteoclasts, which are cells that break down bone tissue.
4. It promotes renal excretion of calcium and phosphate, reducing their levels in the bloodstream.
5. Calcitonin's effects are generally opposite to those of parathyroid hormone (PTH).

Review Questions

• Which gland produces calcitonin?
• What is the main function of calcitonin in regulating calcium levels?
• How does calcitonin affect osteoclast activity?

Related terms

Parathyroid Hormone (PTH): A hormone released by the parathyroid glands that increases blood calcium levels by stimulating osteoclast activity and decreasing renal excretion of calcium.

Thyroid Gland:

An endocrine gland located in the neck that produces hormones such as thyroxine (T4), triiodothyronine (T3), and calcitonin.

Osteoclasts:

Cells responsible for bone resorption, breaking down bone tissue to release minerals into the bloodstream.