A 30-year-old woman from East Anglia has been diagnosed with gigantomastia, a rare condition causing rapid breast tissue growth, after her breasts enlarged while taking the weight-loss drug Mounjaro. Tianna Moon, a content creator, lost three stone after starting Mounjaro in May 2024, but her breasts grew from an L cup to an M cup instead of shrinking.
Moon researched her symptoms online and visited her GP in July 2025, who confirmed gigantomastia. She struggles to find bras, often buying the largest size available and 'making it work,' which has caused cuts and infections under her ribs. Over the past six months, she has stopped wearing bras due to pain.
She has been referred for physiotherapy and underwent a private gastric sleeve surgery in November 2025 to protect her back from further pain. Despite losing two more stone, her breasts have continued growing to a 34NN cup. Moon says she cannot lie on her back for long periods due to restricted airflow.
Moon, who started an OnlyFans account in 2021 after a head injury, now earns around £10,000 a month from admirers. She is considering breast reduction surgery but notes there is no guarantee the tissue won't grow back.
