When is a Pentagastrin Test Advised in Following MTC?

Question

I would like to see more information about the use of pentagastrin-stimulated CT secretion as a test to determine whether thyroidectomy is to be recommended in persons with the C609Y (or other relevant location) mutant RET proto-oncogene on chromosome 10. It appears that some physicians recommend thyroidectomy in such a case without ordering the test. The only place where I see it briefly mentioned in the ThyroidManager web site is Chapter 18.

Yours,

L. David Roper

Response

Dear Dr. Roper-

I received your question about the utility of pentagastrin test in patients with C609Y ret mutation. This mutation has been reported in association with familial isolated medullary thyroid cancer (FMTC). As is the case with mutations in other codons associated with FMTC, the consensus agreement proposed in several congress of the MEN 2 study group is that pentagastrin test it is always advise in gene carriers of FMTC to ascertain whether some minimal disease is already present. If a significant response of calcitonin to pentagastrin stimulation is present (or if some other clinical features are suspicious) thyroidectomy is advise. If not, thyroidectomy may be delayed, although some authors prefer to propose surgery even if pentagastrin test is negative. I hope that this clarification may answer your question.

Sincerely,

F. Pacini MD