Overview and Clinical Significance
Calcitonin is a hormone produced by the thyroid gland, specifically by the parafollicular (C) cells. It plays a role in calcium homeostasis, though its physiological importance in humans is relatively minor compared to parathyroid hormone (PTH) and vitamin D.
Clinical Significance
- Calcium Regulation: Calcitonin lowers blood calcium levels by inhibiting osteoclast activity, reducing bone resorption.
- Medullary Thyroid Cancer (MTC): Elevated calcitonin levels are a key marker for medullary thyroid carcinoma, aiding in diagnosis and monitoring.
- Paget’s Disease of Bone: Historically used as a treatment to reduce bone turnover, though newer medications have largely replaced it.
- Hypercalcemia Management: Occasionally used to lower dangerously high calcium levels, particularly in malignancy-related hypercalcemia.
- Limited Physiological Role: Unlike PTH, calcitonin’s role in calcium balance is not essential, and its absence does not cause significant clinical effects.
Calcitonin testing is primarily used in thyroid cancer diagnostics and bone metabolism disorders.