GCG and thyroid cancer: Reducing portions sizes and avoiding fatty foods may also help.42,51–54,59–61,66 These GI side effects, along with slow gastric emptying, cannot, however, be considered responsible for the drug's effect on weight loss.66 Like the other GLP-1 RAs, semaglutide has a black box warning for medullary thyroid carcinoma (although thyroid cancers have not been reported in human trials) and should not be used in patients with a personal or family history of medullary carcinoma or multiple endocrine neoplasia syndrome.