Woman's Breasts Grew to 34NN on Mounjaro, Diagnosed with Rare Gigantomastia
Tianna Moon, a 30-year-old woman from East Anglia, has revealed a startling medical journey after her breasts grew to a 34NN cup size while taking the weight loss medication Mounjaro, leading to a diagnosis of a rare condition called gigantomastia.
Unexpected Growth During Weight Loss
In May 2024, Tianna decided to lose weight using Mounjaro, starting at 19 stone. Over the course of a year, she successfully lost three stone, but instead of her breasts shrinking as expected, they grew from an L cup to an M cup. She described this as "odd" and concerning, prompting her to investigate further.
Through online research on medical discussion groups and Chat GPT, Tianna stumbled upon information about gigantomastia, a rare condition characterized by rapid breast tissue growth. In July 2025, her GP confirmed the diagnosis after reviewing her medical history, weight loss on Mounjaro, and the unusual growth pattern.
Daily Struggles and Physical Pain
The condition has brought significant challenges to Tianna's daily life. Finding a bra in her size is impossible, as bras in NN cup do not exist commercially. She has resorted to buying the largest available sizes and "making it work," which has led to cuts and infections under her ribs. Over the last six months, she has stepped away from wearing bras entirely due to the pain, stating she is "happier without them."
Physical symptoms include numb arms, severe indentations on her shoulders, and light scarring from bra rubbing. Lying on her back is difficult as it restricts airflow. To manage pain, she has been referred for physiotherapy and underwent a private gastric sleeve surgery in November 2025 to protect her back from further issues.
Continued Growth and Social Impact
Despite further weight loss of two stone, her breasts have continued to grow to an NN cup. Tianna attempted to weigh them using normal scales, estimating one breast at 1st 13lb and the other at 1st 12lb, though she acknowledges the accuracy is uncertain.
Growing up with a larger chest, Tianna faced unwanted attention, recalling incidents as a teenager where grown men would leer and honk horns. As an adult, this has normalized to the point where she often doesn't notice people staring or pointing in public, such as during a trip to Amsterdam for an awards ceremony.
Career and Online Backlash
After a head injury in 2021 left her unable to work full-time, Tianna began an OnlyFans career, now earning an average of £10,000 per month from admirers of her bust. She views this as "reaping the benefits" of her condition rather than focusing on the negatives.
However, she faces a crazy amount of online criticism, with people accusing her of lying about her diagnosis, calling it disgusting that she hasn't had a reduction, and claiming she is begging for attention. Tianna responds by emphasizing the reality of her condition and the lack of guarantees that breast reduction surgery would prevent regrowth.
Medical Context and Future Plans
Gigantomastia is distinct from the less severe condition macromastia, which involves more gradual breast enlargement. Tianna's early diagnosis was facilitated by the unusual growth pattern not aligning with other conditions.
Now weighing 14 stone, she is considering breast reduction surgery but notes there is "no guarantee" her breast tissue won't grow back. Her journey highlights the complex interplay between medication, weight loss, and rare medical conditions, underscoring the need for awareness and support for those affected.
