S4100 Iron Deficiency Anemia and Weight Loss: A Case of Colon Cancer in a Young Woman on Semaglutide

Introduction: Semaglutide is commonly prescribed for obesity and type 2 diabetes to promote weight loss. While beneficial for many patients, the weight loss it causes can sometimes complicate the diagnostic process. We present the case of a 26-year-old woman whose diagnosis of colon cancer was delayed because her symptoms were misattributed to her menstrual cycle and semaglutide use. Case Description/Methods: A 26-year-old woman with a history of iron deficiency anemia presented for evaluation of worsening anemia. Her labs showed an iron percentage of 3% and hemoglobin (Hb) of 6.1 g/dL. She reported intermittent cramping lower abdominal pain for 6 months, melena, lightheadedness, tenesmus, nausea, and weight loss, which she attributed to semaglutide injections. She denied experiencing any other symptoms or having a family history. On a previous hospitalization for anemia, she underwent an endoscopy that only showed mild gastritis. She had no prior colonoscopy. Upon admission, the patient had microcytic hypochromic anemia and mild leukocytosis. She was tachycardic but normotensive. A computed tomography abdomen and pelvis showed mucosal thickening in the transverse colon, suggestive of colitis. A fecal occult blood test was negative, and her fecal calprotectin was elevated. CRP and ESR were both normal. Tumor markers were negative and a gastrointestinal PCR was negative. The patient underwent a colonoscopy that revealed a 7-cm fungating transverse colon mass, consistent with malignancy. Pathology revealed adenocarcinoma. She underwent a staging work-up, which showed no evidence of metastasis. The patient ultimately elected to undergo a right-sided hemicolectomy in the outpatient setting. Discussion: While the benefits of semaglutide are well-documented, it is associated with side effects such as nausea, vomiting, gastrointestinal discomfort, and a potential link to pancreatitis. Some studies suggest that semaglutide may have a protective effect against colorectal carcinoma, given its weight loss and anti-inflammatory effects. However, cancer-related weight loss is one of the most common early signs of malignancy. Given that Semaglutide causes weight loss, distinguishing medication-induced weight loss from malignancy-related weight loss can be challenging. While colorectal cancer is less common in premenopausal women, its incidence in young patients has risen. Iron deficiency anemia should not be quickly attributed to menstruation. In such cases, colonoscopy remains the gold standard for colorectal cancer screening.