Give your feet a little more credit. Here’s how they can alert you to serious issues like diabetes, thyroid disease, and heart disease before you can even get to the doctor’s office.

Dry, flaky feet

Thyroid problems alert, especially if moisturizer doesn’t help. “Thyroid problems cause severe dryness of the skin,” says Marlene Reid, DPM, a foot specialist in Naperville, Illinois.

Brittle toenails can also signal thyroid complications. Here are some healthy habits for a happy thyroid.

Bald toes

If the fuzz on your toes suddenly disappears, it could signal poor blood circulation caused by peripheral arterial disease (PAD). “Signs of PAD can include decreased hair growth on the feet and ankles, purplish toes, and thin or shiny skin.

A buildup of plaque in the leg arteries, PAD affects about 8 million Americans. Symptoms are subtle, but doctors can check for a healthy pulse in the foot or spot PAD on an X-ray.

Ulcers that don't heal

Uncontrolled glucose levels can damage nerves and cause poor circulation, so blood doesn’t reach the feet. When blood doesn’t get to a wound caused by, say, irritating shoes, the skin doesn’t heal properly.

Other signs of diabetes may include tingling or numbness of the feet. Ask your doctor about getting your blood sugar levels tested.

Enlarged, painful big toe

Foods high in purine, a chemical compound found in red meats, fish, and certain alcohol, can trigger an attack by raising levels of uric acid in the body.

Good news is that uric acid is normally excreted through urine, but is overproduced or under-excreted in some people

Tiny, red lines under the toenail

Red streaks underneath the toenails or fingernails could be broken blood vessels known as splinter hemorrhages. These occur when small blood clots damage the tiny capillaries under the nails. They can signal endocarditis, an infection of the heart’s inner lining.

The infection can result in heart failure if left untreated. If you notice splinter hemorrhages on your toenails or fingernails, and haven’t experienced any recent trauma to the nail, see your doctor to check your heart and blood circulation.

Clubbing

Lung cancer and heart disease decrease vascular resistance, which means blood flow to the small arteries in the toenails and fingertips will increase. Tissue swells and results in the “clubbed” appearance (rounder, wider fingers and toes). Though patients are typically aware they have a disease that is causing the clubbing, it’s best to get checked if you see any abnormalities. (

Pitted toenails

If you find tiny holes, grooves, or ridges in your toenails, you may have nail psoriasis. Though most people who experience nail psoriasis also have skin psoriasis (an autoimmune disease that makes skin patchy and irritated), 5 percent of people with nail psoriasis aren’t affected elsewhere.

Spooned nails

Do you have a depression in the toenail deep enough to hold a water droplet? Also known as koilonychias, spoon-shaped toenails or fingernails can indicate iron deficiency, as well as hemochromatosis (overproduction of iron), Raynaud’s disease (which affects blood supply to the fingers and toes), and sometimes lupus (an autoimmune disease in which the body’s immune system attacks cells, tissues, and organs).

Straight line under your toenails

A dark, vertical line underneath a toenail could be a form of the skin cancer that appears on obscure body parts “It will be a black line from the base of your nail to the end of the nail,” says Pichney. “It should be seen by a podiatrist or dermatologist. You want to make sure it’s not fungus, which is usually yellow brown and sporadic throughout the whole nail.”

A suddenly high arch

Thinning arch muscles is an inherited disorder that damages the peripheral nerves (those outside the brain and spinal cords), This condition can also cause changes in gait, numbness in the feet, difficulty balancing, loss of muscles in the lower legs, and later on, similar symptoms in the arms and hands.

—rd