Calcitonin

Overview

• Synthesis 
  • made in parafollicular cells (C cells) of thyroid in response to hypercalcemia
    • inferior parathyroid glands derived from the 3rd pharyngeal pouch
    • superior parathyroid glands derived from the 4th pharyngeal pouch
    • parafollicular C cells derived from ultimobranchial body (4th/5th pharyngeal pouch)
      • originally thought to be of neural crest in origin but are now considered to be a derivative of endoderm
• Function
  • ↓ serum Ca²⁺ via 
    • ↓ bone resorption
    • PTH antagonism
  • not essential in normal Ca²⁺ homeostasis
  • can be used in management of osteoporosis or hypercalcemia (not first line for either)
• Pathology
  • medullary carcinoma of the thyroid
    • parafollicular C cells overproduce caltonin creating sheets of cells in an amyloid stroma
    • stains with Congo red
    • associated with MEN 2A and 2B (mutation in RET)