Calcitonin

Definition

Calcitonin is a hormone produced by the parafollicular cells (C cells) of the thyroid gland that helps regulate calcium levels in the blood. By lowering blood calcium levels, calcitonin plays a crucial role in bone health and calcium homeostasis, counteracting the effects of parathyroid hormone and supporting the balance of calcium metabolism in the body.

5 Must Know Facts For Your Next Test

1. Calcitonin decreases blood calcium levels primarily by inhibiting osteoclast activity, reducing bone resorption.
2. In addition to its role in calcium regulation, calcitonin can also influence kidney function by promoting calcium excretion.
3. The secretion of calcitonin is stimulated by high blood calcium levels, acting as a feedback mechanism to maintain calcium homeostasis.
4. Calcitonin has therapeutic uses, including treatment for conditions like osteoporosis and Paget's disease, where bone density needs to be preserved or increased.
5. While calcitonin plays an important role in calcium regulation, its overall effect is less significant compared to parathyroid hormone and vitamin D.

Review Questions

• How does calcitonin function in relation to parathyroid hormone in regulating blood calcium levels?
  • Calcitonin functions by lowering blood calcium levels when they are elevated, primarily through inhibiting osteoclasts which break down bone and release calcium into the bloodstream. In contrast, parathyroid hormone (PTH) raises blood calcium levels by stimulating osteoclast activity and promoting renal absorption of calcium. This dynamic creates a balance between these two hormones to maintain homeostasis, with calcitonin acting as a counter-regulatory mechanism to PTH.
• Discuss the physiological effects of calcitonin on bone metabolism and kidney function.
  • Calcitonin primarily affects bone metabolism by inhibiting osteoclasts, leading to decreased bone resorption and a reduction in the release of calcium into the bloodstream. This action promotes bone formation and helps maintain bone density. In the kidneys, calcitonin encourages the excretion of calcium in urine, which further assists in lowering blood calcium levels. Together, these effects contribute to overall calcium homeostasis and bone health.
• Evaluate the clinical significance of calcitonin in managing diseases like osteoporosis and how it compares to other treatments.
  • Calcitonin is clinically significant for managing osteoporosis as it helps slow down bone loss and preserve bone density by inhibiting osteoclast activity. It is often administered as a nasal spray or injection. Compared to other treatments such as bisphosphonates or hormone replacement therapy, calcitonin may be less effective as a first-line treatment but can be beneficial for patients who cannot tolerate other medications. Its role in therapy illustrates the complexity of managing osteoporosis and highlights the need for personalized treatment strategies.

Related terms

Parathyroid Hormone (PTH): A hormone secreted by the parathyroid glands that increases blood calcium levels by promoting the release of calcium from bones, reabsorption in the kidneys, and absorption in the intestines.

Thyroid Gland: An endocrine gland located in the neck that produces hormones such as thyroxine, triiodothyronine, and calcitonin, which regulate metabolism, growth, and development.

Osteoclasts: Bone cells responsible for bone resorption, breaking down bone tissue to release calcium into the bloodstream, counteracting the actions of calcitonin.