A woman from East Anglia, England, has been diagnosed with gigantomastia, a rare medical disorder that leads to excessive and rapid breast enlargement. Tianna Moon, age 30, first noticed something unusual when she began to lose weight after starting a prescription medication called Mounjaro, but her breasts continued growing.
Moon had always experienced above-average breast size since puberty. It was only after her weight loss with Mounjaro—an FDA-approved drug that helps manage type 2 diabetes and supports weight loss—that she realized her breast growth was not normal. Doctors considered other conditions such as macromastia, which also causes breast enlargement but is less severe. Eventually, her medical team determined that Moon was suffering from gigantomastia.
According to experts, gigantomastia may be triggered by a variety of factors, such as hormonal changes, genetics, or autoimmune disorders. The Cleveland Clinic reports that there are only about 300 known cases of this condition worldwide. Moon said her breasts currently weigh around 39 pounds, making up about 20% of her total body weight.
Living with gigantomastia brings several difficulties. Moon described having frequent numbness in her arms and deep marks on her shoulders from bra straps. She has also suffered from skin irritation and scarring where her bras rub against her body. Additionally, she mentioned trouble lying on her back for extended periods, as it can affect her breathing. In public, Moon tries to make her breasts look smaller and keep them supported, but she still receives unwanted attention and stares.
While breast reduction surgery is an option to relieve her symptoms, Moon explained there is no guarantee that the breast tissue will not grow back. She said she sometimes faces harsh comments from people who do not understand her condition but chooses to focus on managing her day-to-day life. Moon has even found a way to turn her medical challenge into an opportunity by using online platforms to support herself financially and build confidence in her body type.
