An insurance agent by day, and a high-action casino dealer at Las Vegas' MGM Grand Casino by night, Sandra Yep-Lebeck, 44, knew that her immaculately manicured nails were an integral part of her image. Yet, despite her glamorous exterior, Lebeck was sick, evidence of which lay concealed beneath those perfectly polished nails. During a weekly manicure appointment, Lebeck's nail technician commented on her brittle nails and the separation of the nail bed from her skin, medically referred to as "Plummer's nail". "I decided to use acrylic nails to prevent the green felt at the casino from getting trapped under my nails, and to hide my nail problems from my insurance clients," recalls Lebeck, who now lives in Hong Kong. As her nail condition worsened, she became increasingly sensitive to heat, her neck began to bulge and she experienced hair loss. In 2000, Lebeck was diagnosed with Graves' disease, an autoimmune disorder that leads to an overproduction of thyroid hormones - hyperthyroidism. While symptoms can include enlargement of the thyroid gland (goiter), weight loss and frequent bowel movements, it was Lebeck's nails that first indicated an underlying health condition. "Nails and surrounding tissue can tell you a lot about a person's health," explains Alexandra Duff, podiatrist at PhysioMotion in Central. "Our nails are made of keratin, a hardened protein. Like hair, when you are healthy your nails look good but when unwell, they become brittle and damaged." Duff checks for changes in her patients' nail shape, contour, texture and colour at every consultation. Discolouration under the nail can indicate rheumatoid arthritis, bacterial infections, tumours, Reiter's syndrome (a form of arthritis), liver cirrhosis, or malignant melanoma, a deadly form of skin cancer, she says. While discolouration of the nail plate may simply be caused by nicotine stains or excessive use of nail varnish, it can also indicate fungal or bacterial infection, ulceration, Darier's disease (a rare inherited skin condition), lymphoedema (swelling of body parts due to excess accumulation of protein-rich fluid) and nutritional deficiencies. As a photographer Sara Young, 35, relies on her hands. Yet, she recalls a time when she hesitated to pick up her camera and draw attention to her hands and nails. "I was 16 weeks pregnant when my nails began to turn white. There were purple bits, too," Young says. "Towards the end of my pregnancy, my whole nail was white. I knew that there was nothing wrong with the baby, but there was something wrong with me." Following a blood test, Young learned that she was calcium deficient, and her baby was taking her back-up resources. She was prescribed calcium and magnesium supplements for the duration of her pregnancy and gradually her nail plate returned to normal. "The condition of your nails can highlight numerous nutritional deficiencies," says Jennifer Sheppard, founder of Downtown Detox, a company that provides tailor-made nutritional cleansing programmes. Deficiencies in protein or vitamin B can cause fragile nails, she says. Spoon nails with vertical ridges can indicate iron deficiency, and dry, dark and rounded nail ends can suggest vitamin B12 deficiency. "If you are vitamin deficient, it's best to obtain nutrients from fresh food and then take quality health supplements," says Sheppard. According to Duff, discolouration of the lunule - the crescent-shaped whitish area at the base of the nail - can be scarring from injury or a sign of congestive cardiac failure, malignant melanoma or alopecia (hair loss). As Lebeck discovered in 2008, alopecia can also cause textural changes to the nail. "Seven months after my son was born, my hair started to fall out. I had put this down to hormonal changes but then I noticed deep ridges and white spots in my nails close to the cuticles," she says. Lebeck's endocrinologist confirmed that she had alopecia caused by her thyroid condition. He advised her to let it run its course. "It was only when the ridges in my nails grew out and the deep grooves disappeared that I knew that I was getting better," she says. According to Duff, deformity of the nail plate can indicate eczema, anaemia, dermatitis, cardiac insufficiency and chronic lung disease. Abnormalities around the nail can be caused by nail biting and cosmetic damage or paronychia (infection or inflammation of the surrounding skin), epithelioma (malignant changes to the skin), onychocryptosis (ingrown toenail) and peripheral vascular disease. "If you notice changes to the condition of your nails or the surrounding skin, seek advice from a podiatrist or dermatologist," says Duff. "I have seen clubbing of the nails where the patient turned out to have lung cancer. I have also seen melanomas, ulceration and gangrene under the nails. Catching these early can be a life-saver." Lebeck, who continues to enjoy fortnightly manicures, stresses the importance of looking beyond aesthetics. "I have learned from my two medical situations to always check my nails," she says.