My double N-cup boobs won’t stop growing due to a rare condition

Charlie Sawyer

Published February 2, 2026 2:32pm Updated February 2, 2026 6:39pm

Tianna Moon was diagnosed with a rare condition that affects only 1 in 100,000 people (Picture: Tianna Moon/SWNS)

When Tianna Moon was just 13 years old, she says it was standard for men leer at breasts, honking their horns as she walked home from school.

‘It’s become so normal to me, I don’t even notice it anymore,’ she says.

‘When I go out in public I try and make then smaller than they are and strap them up – I get stares and double takes.’

Now, aged 30, Tianna measures in at a 34NN, and at 14st, she carries around 2st 11lb of that weight on her chest.

Now, she’s learnt the case of her unusually large breasts, after being diagnosed with a rare condition called gigantomastia, a severe form of macromastia, which causes excess breast tissue to grow rapidly.

Tianna, from East Anglia, only learnt of her condition when she began taking weight-loss drug Mounjaro, and noticed that, while her body was getting slimmer, her breasts were actually growing.

Tianna Moon. // A woman has told how her natural 34NN cup breasts will not stop growing due to a rare condition. Tianna Moon, suffers from gigantomastia ? a rare condition which causes rapid breast tissue growth. She says it ?could be possible? she has the biggest boobs in Britain and does not know any other women with gigantomastia. Finding a bra is impossible for Tianna with the largest size she can find leaving her with cuts and infections under her ribs. Photo released 02/02/2026 — The 30-year-old has become a popular adult content creator (Picture: Tianna Moon / SWNS)

Having had large breasts since her teens, Tiana reels off a long-list of challenges that come with them.

‘The side effects are having numb arms quite a lot and having quite severe indentations on my shoulders,’ she explains.

‘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.’

Tianna also adds that ‘bras are impossible’ to find, saying she is left buying the biggest possible bra she can find, and ‘making it work’.

But it was only when she started taking Mounjaro in May 2024, that she finally started to get some answers. In a year, she quickly lost three stone – but in that time, her breasts grew from an L cup to an M cup.

Noticing that it was ‘odd’ her boobs were growing at such a fast pace, she started searching online in medical discussion groups. After doing some digging, she eventually ‘stumbled across’ gigantomastia, which seemed to match her symptoms more closely.

And, a visit to her GP in July 2025 confirmed her own suspicions.

‘Originally he was looking at macromastia but when I broke down medical history, the weight loss on Mounjaro and the increased growth and side effects, he was point blank like “this is gigantomastia”,’ says Tianna.

With only 300 cases recorded, Tianna joins a small group of people afflicted with this condition.

However, Tianna has decided to use her larger breasts to her advantage.

Already an OnlyFans model, after joining the site in 2021 when a head injury left her unable to work, Tianna now makes £10,000 a month off admirers of her fuller bust.

‘I might as well try and reap the benefits of my medical condition rather than the negatives,’ she explains.

In fact, she adds ‘as [my boobs] got bigger it was actually a subscriber who said you need to get remeasured because you are not the size say you are. That’s when I stared monitoring them.’

But not all the attention she receives in positive.

She said: ‘People are telling me it’s disgusting I’m not having a reduction and that I’m basically begging for attention.’

Tianna has looked into a breast reduction, but says there is ‘no guarantee’ her breast tissue won’t grow back.

She underwent a gastric sleeve in November 2025 to help ‘protect her back’, and has been referred for physiotherapy to help with any further pain.

‘When I was younger I hated the attention but now I just think they could be a potential buyer, and my subscribers aren’t creepy, they genuinely love my breasts and support me.’

O-cup breasts: 'I swim a lot because I’m weightless so it’s a relief'

Metro recently also spoke with Summer Robert, 25, another young womanwith gigantomastia.

Measuring in at around a 30N or 28 O-cup breast size, depending on the shop, Summer carries around approximately 25kg of weight on her chest every day.

Having been refused a breast reduction due to her BMI, Summer has pursued an OnlyFans career, growing a loyal following who support her and help her feel confident in her skin.

In order to cope with the excess weight of her breasts, Summer wears a doctor-prescribed corset.

?400 bras and distracted teachers, my life with 25kg breasts that?won?t?stop growing picture: Supplied — Summer has faced harassment from men all her life, and claims she was sexualised by her teachers (Picture: Supplied)

‘I’ve worn one since I was 16 because if I’m walking my back feels like it’s broken – it’s so intense and painful,’ she says. ‘If I’m washing up or cleaning my house, I have to wear a bra because of the sheer weight of them.

‘I swim a lot because I’m weightless so it’s a relief, but then I get out the pool and it feels horrific.’

She can’t go to the gym, go for a run, or find a bra that doesn’t cost her £400, but despite these drawbacks, Summer has turned her large breasts into a positive.

To learn more about Summer’s story, read Metro’s full interview.

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