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Large hands and feet

You would worry, and rightly so, if a loved one developed a protruding jaw, a prominent forehead, and out-of-proportion hands and feet. All are classic signs of acromegaly, a hormonal disorder that occurs in adults when the pituitary gland makes too much growth hormone.

But would you notice the person's change in appearance? Because it's such a rare disorder—and because changes in bone and soft tissue occur slowly over time—it doesn't dawn on people and often goes undetected, says Andrea Utz, MD, PhD, director of the Vanderbilt Pituitary Center at Vanderbilt University Medical Center in Nashville.

Next: Dark skin patches