Dame Maggie Smith, national treasure and star of Hollywood films including Sister Act and the Harry Potter series, has died aged 89.

In a statement, the Oscar-winning actor's family said she 'passed away peacefully in hospital early this morning' — but did not confirm her cause of death.

The Downton Abbey star enjoyed an incredible 70-year long career on stage and screen. 

But the beloved star was no stranger to health struggles, having lived a life peppered with illnesses which she candidly discussed. 

She suffered two major health scares during her professional career, one of which left her in a 'fog of despair'. 

Grave's Disease

In January 1988, Dame Maggie was diagnosed with Graves' disease, an autoimmune condition that mainly affects young and middle-aged women. 

It occurs when the immune system produces antibodies that cause the thyroid to produce too much thyroid hormone, according to the NHS.

Around 80 per cent of people with an overactive thyroid gland are believed to have it.

The cause is unknown, but it often runs in families. Smoking can also increase your risk of getting it.

Symptoms can include irritability and swings in emotion, nervousness or anxiety, weight loss, heart palpitations and sweating or feeling hot.

Shaking and tremours, poor sleep, muscle weakness and difficulty getting out of chairs or climbing stairs, are other key signs. 

In women, periods may also become light or stop altogether. 

In a 1990 New York Times interview, she revealed her eyes became irritated and protruded with puffiness around them, which she said looked 'absolutely frightening'.

Talking about the onset of the condition, which followed a cycling injury that broke her arm, she said: 'It's been kind of like a fog of despair, really.

'It was ghastly having a broken arm, ghastly with the play, letting everybody down and on top of that, I looked absolutely frightening, and didn't know which way to turn.'

Dame Maggie underwent radiotherapy and optical surgery to treat her condition – and was put into isolation for 12 months during recovery.

Breast Cancer  

In 2007, while filming Harry Potter and The Half-Blood Prince she was diagnosed with breast cancer. 

She was given the all-clear after two years of treatment.

One in seven women in the UK are diagnosed with breast cancer in their lifetime — around 56,000 a year — making it the most common cancer in the UK. 

The figure stands at roughly 300,000 annually in the US. 

Between 85 to 90 per cent of women diagnosed with primary breast cancer survive more than five years.

However, secondary breast cancer — or stage four — which accounts for around 16 per cent of all breast cancers in the UK and US, is far more difficult. 

It means the cancer, that started in the breast has spread to another part of the body, commonly the liver, lungs, brain or bones. 

In 2009, after revealing her diagnosis she admitted the illness had 'knocked her sideways'. 

She said: 'It kind of takes the wind out of your sails, and I don't know what the future holds, if anything. 

'I don't think there's a lot of it, because of my age — there just isn't. It's all been. I've no idea what there will be.'

Speaking about the treatment that she received, she said that she was 'hairless' and felt 'horribly sick' from chemotherapy.

Heart troubles 

In November 2012 Dame Maggie was forced to dismiss rumours she was at the centre of a heart scare. 

She was reportedly admitted to a specialist cardiac unit complaining of severe pains. 

But the actress underwent a series of emergency tests at the private Wellington Hospital in London, and was discharged later the same day according to the Sunday Mirror. 

It is thought the reports emerged after Dame Maggie visited her doctor for a routine medical procedure. 

At the time her spokeswoman said: 'She is fine and well and at home.'

Glaucoma 

At the age of 77 Dame Maggie became a patron of the International Glaucoma Association, now known as Glaucoma UK. 

Around the same time it emerged she had the condition herself.  

Glaucoma is usually caused by fluid slowly building up in the front part of the eye, which increases pressure inside it.

As a result, the optic nerve, which connects the eye to the brain, becomes damaged.

Around 700,000 people in the UK and more than 2million in the US are living with glaucoma, which is usually symptomless in its early stages.

It mostly affects those in their seventies and over, but people of any age can get it.

Eye pain, blurred vision and vomiting are all tell-tale signs of an incurable condition known as the 'silent thief of sight'.

However, the symptoms of glaucoma, which affects two per cent of over-40s in the UK, can vary considerably.

They can range from cloudy vision and teary eyes to vomiting. 

Glaucoma, which develops slowly over many years in most cases, can lead to a loss of vision if not treated promptly. 

Treatment aims to lower this pressure through prescription eye drops, oral medicines, laser retreatment, surgery or combination of these options.