Calcitonin

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.

Increasing +

Decreasing -

Medullary Thyroid Carcinoma

  • A classic cause of markedly elevated calcitonin.

Thyroid or Parathyroid Disorders

  • Occasionally, other thyroid pathologies or systemic calcium dysregulation can raise calcitonin levels.

Rare Inflammatory Effects

  • In specific cases, severe systemic inflammation might induce modest elevations in calcitonin.

Generally Normal

  • Low calcitonin is not usually of clinical concern given its secondary role in calcium balance.

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Related

Pediatrics

  • Levels are generally low; abnormal elevations are unexpected.

Adulthood/Elderly

  • Elevations become particularly concerning for thyroid cancer or endocrine dysregulation.

Thyroid Function

  • Common Thyroxine (T4), Free Thyroxine (FT4), Free Triiodothyronine (FT3):
    These markers measure the overall thyroid hormone production and the bioavailable (active) fractions. While Common T4 reflects total hormone levels (both bound and free), FT4 and FT3 specifically indicate the unbound, active hormones that drive metabolic processes.

  • Thyrotropic Hormone (TSH):
    This pituitary hormone regulates thyroid hormone synthesis through a negative feedback mechanism. Elevated or suppressed TSH levels provide insight into thyroid function and help direct further evaluation of thyroid disorders.

  • Thyroxine Binding Globulin (TBG):
    TBG is the main protein binding thyroid hormones in the blood. It influences the proportion of hormone that remains free versus bound, affecting the interpretation of Common T4 compared to FT4 and FT3 levels.

  • thyreoglobulin;calcitonin; tumerous marker thyreoglobulin:
    These markers focus on thyroid tissue activity and neoplastic surveillance.


    • thyreoglobulin reflects the functional activity of thyroid follicular cells.
    • When used as a tumour marker (tumerous marker thyreoglobulin), it helps monitor for residual or recurrent differentiated thyroid cancer following treatment.
    • calcitonin, secreted by the thyroid’s C cells, is particularly valuable in detecting medullary thyroid carcinoma.

Together, these markers offer a comprehensive view of thyroid gland function, regulation, and tissue integrity, integrating hormonal activity with diagnostic tools for thyroid cancer surveillance.

All Markers