Researchers at the University of Illinois Chicago analysed data from 527 patients who took tirzepatide – Eli Lilly’s popular weight‑loss drug – for one year. They found that 5.3% of patients developed new thyroid problems or experienced worsening of pre‑existing conditions. The most common diagnoses were nodular goitre and drug‑induced thyroiditis.
The scientists identified two main factors that increase the risk of such complications. The first is severe (end‑stage) kidney failure, which nearly triples the likelihood of thyroid problems. The second is a pre‑existing thyroid disorder before starting the drug, which more than triples the risk.
The authors recommend classifying such patients as high‑risk. They advise regular monitoring of thyroid hormone levels, calcitonin and kidney function – both before starting treatment and during therapy. Genetic testing may also be required in some cases.
Based on animal studies, tirzepatide had previously been contraindicated in patients with rare inherited syndromes such as medullary thyroid cancer and MEN‑2. The new study suggests the spectrum of potential problems is wider, adding relatively common conditions such as goitre and thyroiditis.
The researchers acknowledge that their study has limitations, being based on medical records rather than a controlled trial. Larger studies are needed, they said. Nevertheless, they recommend that doctors pay closer attention to thyroid function in patients with kidney failure or pre‑existing thyroid disorders when prescribing tirzepatide for weight loss.
In a separate study, US scientists found that taking heartburn drugs (proton pump inhibitors) together with GLP‑1 drugs such as Ozempic or Wegovy increases the risk of gastrointestinal problems, with such patients more often requiring endoscopy.