More Hidden Symptoms Doctors Can Spot 

Hidden Symptom: Rolling an imaginary pill

Could be a sign of: Parkinson's disease

Pill-rolling hand-tremor, where you rub the thumb and forefinger together, is an early sign of Parkinson's.

Even if you notice you're doing it, you probably think of it as a harmless quirk. But, to a competent doctor, this would be a serious warning sign that requires tests.

Parkinson's disease, a degenerative condition where the brain becomes increasingly damaged, affects one in 500 in the UK. The disease affects the parts of the brain that control the hands, which explains this symptom.

Other early hidden symptoms of Parkinson's disease includes: suddenly small handwriting; looking stern or serious (even when not in a bad mood); a blank, unblinking stare; loss of smell; sitting or standing hunched over; a stiff walk, without swinging your arms.

Hidden Symptom: A deeper voice

Could be a sign of: Hypothyroidism

If you, or (more likely) your loved-ones, have noticed your voice has lowered recently, especially if your speech is strangely slow, it could be a sign of the autoimmune disorder, hypothyroidism (an underactive thyroid). The dysphonia (voice change) is caused by the lack of thyroid hormone.

Hypothyroidism can be successfully treated with synthetic thyroid hormone.

However, it's important to get checked-out quickly, as - in rare cases - sudden voice changes can be a sign of throat cancer, destroying nerves and paralysing the larynx until only one vocal cord can move. However, according to Shropshire-based GP, Dr. Roger Henderson, in throat cancer, the voice is usually "whispery", rather than gruff.

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Hidden Symptom: "Clubbed" nails

Could be a sign of: cancer

Clubbing, where the tissue between the nail thickens and nails become bulbous and rounded, is seen in several types of cancer, including lung cancer, stomach cancer and bowel cancer.

Hidden Symptom: Ulcers on the feet

Could be a sign of: diabetes

Unregulated blood glucose levels damage nerves and cause poor circulation, so blood doesn't reach the feet. Small wounds are easily caused by, for example, wearing too-tight new shoes. In diabetes, these don't heal properly and can become ulcerated.

Marlene Reid, foot specialist in Indiana, says: "Many people with diabetes are first diagnosed because of foot problems".

Other foot problems that may be signs of diabetes include tingling or numb feet.

If you notice these symptoms, ask your doctor to check your blood glucose levels.

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Hidden Symptom: Unable to look people in the eye

Could be a sign of: Depression

This is one that others are more likely to notice. If someone feels depressed, they may subconsciously fear there's a stigma to admitting it, and so be reluctant to look other people in the eye.

Another red-flag is when a person bursts into tears or becomes irritable in the middle of a neutral conversation.

Depression disturbs feel-good chemical Serotonin, making the person prone to bouts of tearfulness or irritability. If you find a friend or relative becoming upset, or not looking you in the eye, gently suggest they talk to their doctor.

Hidden Symptom: Veering to the left/right of a chair

Could be a sign of: brain tumour

If, when you sit in a chair, you sit to the very edge of one side, it could be a sign of a potentially-devastating brain tumour. In a brain tumour, your field of vision is disturbed, reducing what you see without your knowledge. This forces you to readjust the way you sit or how you hold your head when you talk to someone.

What do I do?

If you, or your loved-ones, notice that you have any of these symptoms, don't panic. The first thing to do is book an appointment with your doctor to discuss your concerns.

Remember, these symptoms only may be a sign of something serious (and, even then, many of these illnesses can be successfully treated or managed, once diagnosed). In many cases there could also be benign explanations for your symptoms.

Be aware. Be safe. Be calm.