Tianna Moon experienced an unexpected change while on her weight loss journey with Mounjaro. Although she successfully lost three stone, she was surprised to find that her breast size increased rather than decreased. At 30 years old, Moon had always dealt with a larger bust, but after embarking on her weight loss mission in May 2024, her size increased from an L cup to an M cup, marking an inch increase in circumference.
The UK-based content creator noticed the unusual growth in her breasts despite her overall weight loss. It wasn’t until she engaged in online health discussions and consulted ChatGPT that she realized there was a deeper issue. She was diagnosed with gigantomastia, a rare condition that results in a rapid and significant increase in breast tissue. As a result, Moon continues to see her bust size grow, facing challenges in finding suitable bras.
Moon experiences significant discomfort due to her condition, including back pain and skin sores. She attempts to manage by wearing the largest bras she can find, though this leads to cuts and tears under her breasts, which have now grown to a 34NN as she lost an additional two stone. She shared her struggle: “Bras are impossible. Bras in my size NN don’t exist.”
The pain led her to abandon bras altogether, finding relief in going without them. Despite having been diagnosed with gigantomastia in July 2025, she continues to deal with the challenges of her condition. She explained: “The side effects are like having numb arms quite a lot and having quite severe indentations on my shoulders. I have some light scarring under my breasts where bras have rubbed and ripped the skin open. Also laying on my back is not something I can do for a long period of time as it restricts the amount of air flow I can get in.”
After suffering a head injury in 2021 and losing her job, Moon turned to OnlyFans to monetize the attention her size L chest received. During a trip to Amsterdam for the Xbiz awards, she realized the attention had become so routine that she barely noticed it. As she recounted, “It got to the point where last September I was in Amsterdam for the Xbiz awards as I was nominated. I was walking around with another lady and she said, ‘don’t you realise those people are pointing at you and trying to get your attention?’ It’s become so normal to me I don’t notice it anymore.”
When Moon’s weight dropped from 19st to 14st, and her bust grew by three cup sizes, she sought medical advice. Initially considering macromastia, her doctor diagnosed gigantomastia after reviewing her medical history, weight loss, and other symptoms, stating, “this is gigantomastia.”
With her breasts now weighing approximately three stone, Moon experiences daily discomfort. In November, she took measures to safeguard her health by getting a gastric sleeve surgery to alleviate potential back issues. Considering breast reduction surgery, Moon’s OnlyFans venture has proven financially beneficial, earning her around $13,000 monthly. She expressed, “I might as well try and reap the benefits of my medical condition rather than the negatives.” It was one of her subscribers who first prompted her to get remeasured, noticing the growth in her chest. She recalled, “As they got bigger, it was actually a subscriber who said you need to get remeasured because you are not the size say you are.”