Parkinson's UK said it was sorry to hear that Connolly was being treated for a disease that affects around 127,000 people in the UK.
Steve Ford, chief executive of the charity, said: "One person every hour will be diagnosed with Parkinson's in the UK. Despite this it remains a little understood condition and we salute Billy's bravery in speaking out about his condition.
"Many people, with the right medication, continue to live a full and active live with Parkinson's but for some it can be life-changing and it is vital that Billy gets the support he needs to live with this complex condition."
IBTimes UK looks at the degenerative disease
What is Parkinson's
Parkinson's is a degenerative disease that affects the central nervous system. It is a neurological condition where the sufferer does not have enough of the chemical dopamine because nerve cells in the brain have died. Symptoms of Parkinson's normally emerge when around 70% of cells have been lost.
Without dopamine, movements become slower and it takes people with the condition longer to complete physical tasks. Symptoms develop gradually in no particular order. People with Parkinson's often feel tired and week, have trouble with their handwriting and feel tremors in their arms.
The cause of the disease is unknown, although genetics and environmental factors are thought to play some role in its development.
Symptoms and disease progression vary in every person suffering from Parkinson's, but the main physical signs include tremors, slowness of movement and stiffness. Other physical symptoms include bladder and bowel problems, dizziness, restless leg syndrome, sleep problems and trouble with speech and communication.
Sufferers can also present mental health symptoms, including anxiety, dementia, depression, hallucinations and memory problems.
Diagnosis and Types
Parkinson's is difficult to diagnose as there is no laboratory test that can confirm it. Doctors will examine the patient and take a history of any symptoms.
There are a number of different types of Parkinson's. The most common form is idiopathic Parkinson's disease. Disease progression varies from person to person but early diagnosis can help as treatment can begin sooner.
Other forms of the disease include vascular Parkinsonism, thought to be caused by hypertension and diabetes, drug-induced Parkinsonism, which is most often a result of neuroleptic drugs used to treat psychotic disorders, and inherited Parkinson's, which is passed through family members.
Parkinson's is most common in people aged over 50 but one in 20 sufferers is under 40. Juvenile Parkinson's affects people under the age of 20.
Parkinson's symptoms change as the disease develops, with some symptoms becoming worse and others appearing over time.
People with the disease can experience increased problems with movement, making day-to-day life and independence more challenging.
The final stage ir reached when the person is no longer able to undertake tasks such as washing and dressing without help. Drug treatments may become less effective at managing symptoms. Side-effects can outweigh benefits.
Most researchers and doctors do not think that Parkinson's directly causes death and none of the drugs used for treatment can cause death. Life expectancy for Parkinson's sufferers is not significantly affected, but some symptoms can lead to increased disability and poor health, making people more vulnerable to infections.
Most people with Parkinson's use drugs to control the symptoms and treatment is prescribed to suit the individual sufferer. Therapies involve increasing the level of dopamine that reaches the brain and stimulating the area where dopamine works.
Therapy can also be used to help people manage symptoms with exercises and treatments that can help manage the condition. Exercise is recommended to ease rigid muscles and joints.
In some cases, surgery is used to treat symptoms as it can help some people get better control of their symptoms, but not everyone is suitable for surgery.
Parkinson's UK has invested over £60m in researching the disease.
Scientists are looking at gene therapy, which could be used to prevent the death of nerve cells and promote the regeneration of cells. This type of treatment would be used in people in the early stages of the disease, where nerve cells are still alive.
Stem cell research is also being investigated as a potential cure for the disease by restoring the supply of dopamine and making the brain work properly again.
Researchers are looking at how dopamine-producing cells lost in people with Parkinson's can be replaced with new healthy dopamine-producing cells grown in laboratories. It is thought clinical trials using stem cell therapy will only be considered in five to 10 years.
To report problems or to leave feedback about this article, e-mail:
To contact the editor, e-mail: