Basal and stimulated calcitonin levels in patients with type 2 diabetes did not change during 1 year of Liraglutide treatment

BACKGROUND AND AIMS: The administration of Liraglutide, a long-acting GLP-1 receptor (GLP-1R) agonist, is associated with C-cell adenomas and carcinomas in rats. In humans, GLP-1R is highly expressed in C-cells hyperplasia (CCH) and in medullary thyroid cancer (MTC), though no changes in basal serum calcitonin (bCT) levels were recorded in type 2 diabetic (T2DM) patients treated with Liraglutide. To diagnose the possible development of CCH during Liraglutide treatment, we evaluated CT levels stimulated by calcium test (sCT). MATERIALS AND METHODS: bCT and sCT and metabolic and anthropometric parameters were evaluated in 26 T2DM patients at baseline and at 1, 3, 6 and 12 months of treatment. RESULTS: In all patients, bCT remained within the normal range during the entire study period. In females and males, the higher sCT values were reached after 3 months and 1 month, respectively, with a progressive reduction at 6-12 months. The greater decrease of HbA1c values was reached at 3 months, while body weight and waist circumference decreased over the first 4 weeks of therapy. Lipase levels significantly increased, with a peak value at 1 month. CONCLUSION: The chronic administration of Liraglutide did not lead to statistically significant variations in both bCT and sCT. Stimulated CT levels increased, though always below the normal range, during the first 1-3 months of treatment, and progressively decreased to baseline levels. This finding is consistent with the effects recorded at the glycometabolic level, and suggests the possible induction of a drug tolerance involving also the C cells and thus preventing CCH.