🧬 Thyroid Tumor Markers – Calcitonin & Thyroglobulin

1. Calcitonin

• ✅ Fasting Required: Yes (8–10 hours recommended)
• 📍 Produced By: Parafollicular C cells of the thyroid
• 📊 Function: Helps regulate calcium levels (not a major player in humans)
• 🧪 Used For:
  • Early detection and monitoring of medullary thyroid carcinoma (MTC)
  • Screening in MEN 2 syndrome (Multiple Endocrine Neoplasia type 2)
  • Post-surgical follow-up to detect recurrence
• 📈 Elevated Calcitonin:
  • Medullary thyroid carcinoma
  • C-cell hyperplasia
  • Rarely in other neuroendocrine tumors, renal failure, or sepsis
• ✅ Normal Range:
  • Men: <10 pg/mL
  • Women: <5 pg/mL (Ranges vary by lab)
• 🧪 Stimulation test (e.g., with pentagastrin or calcium infusion) may be used if borderline

2. Thyroglobulin (Tg)

• ✅ Fasting Required: Yes (important to reduce variability)
• 📍 Produced By: Normal thyroid follicular cells and well-differentiated thyroid cancers
• 📊 Function: A storage form of thyroid hormones T3 and T4
• 🧪 Used For:
  • Tumor marker for papillary & follicular thyroid cancer
  • Monitoring after thyroidectomy or radioactive iodine therapy
  • Detection of recurrence/metastasis of differentiated thyroid cancer (DTC)
• ⚠️ Should NOT be used as a screening tool in people with normal thyroid glands
• 🧪 Thyroglobulin Antibodies (TgAb) should be tested simultaneously, as they interfere with Tg interpretation
• ✅ Normal Range (after thyroid removal): < 1 ng/mL
  • In patients with intact thyroid: 3–40 ng/mL (not clinically useful for diagnosis)
• 📈 Elevated Tg in absence of thyroid gland suggests recurrence or metastasis

🔬 Comparison Snapshot

🧪 Recommended Conjunctive Tests