A British woman has shared the unexpected health challenges she says began after using the weight-loss medication Mounjaro, claiming her breasts started growing rapidly and have since made everyday life increasingly difficult.
Tianna Moon, who says she now has the largest natural breasts in Britain, revealed that the dramatic increase in breast size has left her struggling with mobility, sleep, posture and daily activities.
According to Tianna, her bra size increased within a matter of months from an L cup to an NN, and now measures 32OO, making even simple tasks challenging.
Speaking about the impact of the condition, she said the summer months have been particularly uncomfortable.
“The hot weather has been far from pleasant. My boobs are like a heat factory and there isn’t really much I can do to keep cool,” she said.
She explained that her enlarged breasts have also affected her balance and visibility while walking.
“Stairs are also a huge problem now. I’m forever tripping up on them. I have to go really slow because I can’t see my feet anymore. It’s ridiculous, but it’s the truth.”
Tianna also described how the condition has disrupted her sleep.
According to her, she frequently wakes up during the night because the weight of her breasts presses against her chest whenever she rolls onto her back.
“Sleeping is something I’m really struggling with. Since losing weight, it’s easier for me to move in my sleep, meaning I end up on my back more. But I keep waking up because the added weight on my chest suffocates me.”
The 30-year-old has been diagnosed with gigantomastia, a rare medical condition characterised by excessive and rapid growth of breast tissue.
Although she briefly considered the publicity surrounding her becoming Britain’s biggest-breasted woman as a positive aspect of her condition, she said her priority is now finding relief from the pain.
“I’m not the biggest in the world, nor do I want to be. I’m in so much pain now.”
She explained that breast reduction surgery may not permanently solve the problem because the glandular tissue could continue growing after surgery.
Tianna also said surgeons may be reluctant to operate because she has thinning skin around the sides of her breasts, increasing the risk of complications and poor wound healing.
She underwent gastric sleeve surgery in November 2025 to lose weight, but despite her overall weight loss, her breasts reportedly continued to grow.
In an effort to manage the physical strain, she has incorporated weight training and resistance exercises into her routine.
“It’s helping me strengthen my spine and improve my posture,” she said.
However, she admitted that the size of her breasts still causes frequent accidents.
“I forget how big they are because I live with them every day. I’m forever knocking things over and walking into objects since I can’t see properly.”
She added that sitting in a vehicle for more than an hour now causes severe upper back pain, forcing her to spend much of her time at home.
While Tianna believes the rapid breast growth coincided with her use of the weight-loss injection, it has not been established that Mounjaro caused her condition. Gigantomastia is a rare medical disorder with several possible causes, and determining whether the medication played any role would require medical evaluation.
