Pentagastrin Test for Medullary Cancer of the Thyroid
Suspected medullary carcinoma of thyroid.
Screening of families with medullary carcinoma of the thyroid.
Patients with suspected MEN type 2. Remember to inform the MEN2 registry.
Allergy/anaphylaxis on repeat administration.
Nausea, epigastric discomfort
Check electrolytes and serum calcium.
Pentagastrin 0.5 mcg/kg body weight.
6 x 7 ml Lithium heparin tubes (green top Vacutainers) with 0.2ml Trasylol added.
Ice or facilities to transfer samples immediately to lab
- Insert cannula and flush.
- Take baseline sample for calcitonin.
- Give bolus i.v. of pentagastrin 0.5 mcg/kg body weight.
- Flush cannula.
- Take samples at 1, 2, 3, 5 and 10 minutes for calcitonin.
- Take immediately to lab on ice.
An abnormal peak calcitonin (> 200 ng/l) is suggestive of medullary thyroid carcinoma and surgical treatment should be considered especially if there is a family history. Potentially affected family members should be screened biennially until 65.
SENSITIVITY AND SPECIFICITY
Pentagastrin stimulates calcitonin best in medullary carcinoma, whereas calcium infusion is best in normals.
Combining two studies only two out of 25 patients with medullary thyroid carcinoma had normal responses to pentagastrin. Many normals have been described with an exaggerated response to pentagastrin and the reproducibility of this test is poor.
McLean G.W. et al., Metabolism 33, 790-796 (1984).