Endocrine Abstracts

Aim: Medullary thyroid cancer (MTC) is 4.73 times higher among glucagon-like peptide-1 (GLP-1) agonist users. GLP-1 agonists are witheld in case of MTC or MEN. Serum calcitonin (Ct) does not increase to diagnostic level in small and nonmetastatic MTC. We report cytology and Ct wash-out results of fine-needle aspiration biopsy of thyroid nodules (FNAB) in type 2 diabetic patients receiving exenatide.

Methods: Eleven male and 66 female patients (31–76 years old) receiving exenatide therapy (5 μg bid for the 1st month and 10 μg bid afterwards) for type 2 DM were evaluated. Serum Ct and Ct wash-out of FNAB were measured using chemiluminescence immunoassay.

Findings: Of 45 patients with basal US evaluation, 19 had micronodules (43%) and 14 had nodules (33%) over 1 cm in size. One patient without baseline value, had Ct level of 482 pg/ml at the 5th month of therapy. She had multinodular goiter on US. Since basal Ct level and FNAB were absent, the relation between high Ct level and exenatide therapy could not be established. The other patients had normal Ct values both at baseline (n=43, 2.26±0.66 pg/ml) and during follow-up (n=65, 2.28±0.62 pg/ml). Three patients developed micro PTC. None of FNAB and histologic evaluation of papillary thyroid cancer (PTC) samples revealed C-cell hyperplasia (CHH). Ct wash-out levels of 21 patients were normal (2.47±1.21 pg/ml).

Conclusion: Effect of GLP-1 analogue on thyroid tissue is still obscure. Normal serum and wash-out Ct levels and FNAB findings suggest exenatide is safe. Because of the index case it may be prudent to do basal US and FNAB as needed at least before therapy. Case it may be prudent to do basal US and FNAB as needed at least before therapy. Levels and FNAB findings suggest exenatide is safe. Because of the index case it may be prudent to do basal US and FNAB as needed at least before therapy and clinical meaning of it is obscure.

Conclusion: Normal serum and wash-out Ct levels and FNAB findings suggest exenatide is safe. Because of the index case it may be prudent to do basal US and FNAB as needed at least before therapy of FNAB and histologic evaluation of PTC samples revealed CHH. Sample of Ct wash-out levels were normal.

Discussion: PTC, MTC, CHH, and normal thyroid tissue bear variable GLP-1 receptors. Whether Ct level will rise along with CHH during GLP-1 analogue therapy and clinical meaning of it is obscure.

Conclusion: Normal serum and wash-out Ct levels and FNAB findings suggest exenatide is safe. Because of the index case it may be prudent to do basal US and FNAB as needed at least before therapy and rule-out any unknown MTC.