Women having breast implants should be warned about a condition linked to chronic pain and extreme fatigue, the British Association of Aesthetic Plastic Surgeons (BAAPS) has said.
Tens of thousands of women on online forums claim they have suffered breast implant illness (BII), of which there is little scientific evidence.
Surgeons, including from BAAPS, are now calling for more research.
The regulator said it monitored issues and would act where appropriate.
Breast implant illness is not an official diagnosis, but some women who believe they have it say they returned to full health after having their implants removed.
The MHRA says there have been more than a million breast implant operations in the UK, and surgeons say most patients are happy with the results.
But a number of women told the Victoria Derbyshire programme they experienced complications which they had not been warned about.
Fitness instructor Naomi Macarthur, 28, decided to get breast implants in 2014, but within weeks she said she began to suffer "the most horrific symptoms".
"I remember getting severe pain in my stomach," she said. "And the tiredness was like I had run a marathon and dug a million trenches and I hadn't done anything. Writing with a pen was too tiring."
As time went on she experienced a long list of symptoms including hair loss, allergies and rashes.
"It's been absolutely horrific," she said, breaking into tears.
Ms Macarthur, who is from Brighton, said doctors repeatedly told her the illness was unrelated to the implants, and at one stage diagnosed her with lupus.
Then, last year, she discovered breast implant illness and found online support groups.
She decided to have her implants removed, and said within days the symptoms which had affected her life for four years began to disappear.
"I can't believe how amazing I feel, and how I have bounced back," she explained. "It's insane."
'Very real for them'
In parts of the medical community there remains scepticism towards breast implant illness.
The BBC spoke to one surgeon - who did not wish to be named - who said he did not believe it was a real condition.
Symptoms reported by those who say they have the illness - mainly related to the immune system - are broad.
They include fatigue, chest pain, hair loss, headaches, chills, photosensitivity, chronic pain, brain fog and sleep disturbance.
This has meant there is currently little evidence that such issues are linked specifically to the implants.
The UK's National Secretary for the International Society of Plastic Surgery, Naveen Cavale, said: "As far as some of my patients are concerned, breast implant illness is a very real thing for them, and I have no reason to doubt them. But, to me, as a doctor, it makes no scientific sense.
"Breast implant illness isn't something we used to always talk about - but the proper plastic surgery associations such as ourselves, have started advising we do so, which I think is a good thing for patients to make more informed decisions."
Consultant plastic surgeon of BAAPS, Nora Nugent, agreed: "Surgeons should be warning patients about breast implant illness. Patients need the most up-to-date information possible, with the caveat that breast implant illness is poorly understood. So it's going to be difficult to give absolute information."
In the US, the Food and Drug Administration (FDA) - the drugs regulation body - has begun to investigate breast implant illness.
Hundreds of thousands of women were affected by the PIP breast implant scandal which broke in 2010.
The implants were twice as likely to rupture and were filled with silicone used in mattresses.
In 2016, a national safety implant register was set up, and women were encouraged to join it so they could be traced if something went wrong in the future.
It is hoped the Breast and Cosmetic Implant Register, which covers implant procedures in England and Wales, will also lead to a better understanding of breast implant illness.
Steph Harris, from Woking, has had three different types of implants, and says on each occasion she experienced symptoms of breast implant illness.
She has previously had breast cancer, but her surgeon and oncologist believe the chronic fatigue and pain are related to the implants.
Ms Harris was forced to leave her job as a nurse because of the effect it had on her.
"To deal with the breast cancer, that was easier. The chemotherapy is easier than the chronic fatigue, I know it sounds weird to say. I guess I'm unique, I have been through both and this is harder."
Ms Harris is now having her implants taken out, and said she was "dreaming" of simple things - like being able to go for a "little walk".
The Medicines and Healthcare products Regulatory Agency (MHRA) received 1,586 Adverse Incident Reports for breast implants between 2014 and May 2019. However, breast implant illness is not officially recognised.
Patients are calling for the MHRA's Yellow Card reporting system to be made more accessible, so the true scale of implant complications are known.
It said in a statement that "patient safety is our highest priority and we always investigate where there are safety concerns raised about a medical device".
It added: "We continue to work with European and international regulators, breast implant registries and experts to monitor issues and will take appropriate safety action where necessary."