CAR T-cell therapy may trigger rare but serious hormone problems like adrenal failure.

When doctors use CAR T-cell therapy to fight cancer, they are essentially reprogramming your immune system. Sometimes, this powerful reset causes your body to react in unexpected ways, including attacking your own hormone glands. A recent look at safety reports from 2017 through the second quarter of 2025 found 14 specific signals pointing to these endocrine problems. The most common issue was high blood sugar, which often showed up when patients were already having a severe immune reaction. Other serious findings included adrenal insufficiency, where your body stops making enough stress hormones, and Hashimoto's thyroiditis, an autoimmune attack on the thyroid. The data also flagged a higher risk of death when these hormone issues occurred together with the severe immune reaction. These findings come from a database of safety reports, not a direct count of every patient, but the pattern is clear enough to suggest real danger.