Loss of smell and frequent urination, and tremors are early signs of parkinsonism. Most doctors concentrate on the major features of Parkinsonism and miss the early subtle features of the disease because non specific health questions were not asked.
A typical scenario of early signs of Parkinsonism might be the following: Many of your friends may have a shaky hand, softening in their speech, and some loss of dexterity. They deny all the problems except the slight tremor. It seems the hand shakes at rest. Their facial expression has changed and seems masked. The voice has become weaker and is softer. When walking the arm with the tremor fails to swing.
When you ask questions you will find that he lost his sense of smell about 6 years ago. He gets up twice a night to urinate and he has been talking in his sleep for several years. He may have hit his wife but does not remember it the next day.
He seems to have a change in mood, and is becoming depressed at times. He becomes anxious at times and has more difficulty concentrating on details at work.
Sure all the above could be due to other causes e.g. sinusitis, possible prostrate enlargement, stress of the job, restless leg etc.
There is no good way to check preclinical Parkinsonism except with expensive PET scans and SPECT tomography.
One can suspect the disease with mood changes, bowel and bladder changes, sleep disturbances, impaired cognitive ability, autonomic and motor changes, and loss of the sense of smell. There may be a mixture of vascular problems, Alzheimer’s, and Parkinsonism.
The symptoms of Parkinsonism vary, as the disease is heterogeneous. Treatment of the dopamine deficiency with levodopa results in dramatic improvement.
Be suspicious and ask your parents questions. You will be the first to make the presumptive diagnosis of Parkinsonism before your doctor is involved