White spots? brittle nails? Hair falling out? Dr Christine Reader looks at what your nails and hair can tell you about your health.   Our hair and nails are constantly growing. Every day is reflected in a tiny bit of growth and, as a result, they can give useful information about many illnesses such as an under active thyroid,  (hypothyroidism), psoriasis or diabetes to name a few. And remember if you are worried, it’s always best to have any changes to your nails or hair health evaluated by a doctor. Before we get onto what your hair and nails can…