Last week Oprah explained on her show that her recent weight gain is due to thyroid disease. In the Oprah magazine she wrote;

My body was turning on me. First hyperthyroidism, which sped up my metabolism and left me unable to sleep for days. (Most people lose weight. I didn’t.) Then hypothyroidism, which slowed down my metabolism and made me want to sleep all the time. (Most people gain weight. I did! Twenty pounds!)

The New York Times had a good article about this on Friday. They note;

Thyroid disorders, which are far more common in women than men, are said to be among the most undiagnosed and misdiagnosed health problems. Part of the problem is that the symptoms are ambiguous and likely to be written off as stress, menopause or normal aging. The most common thyroid problem is caused by an underactive thyroid (hypothyroidism), and symptoms include weight gain, fatigue, depression, high cholesterol, neck pain, hair loss, low sex drive and worsening menstrual symptoms. An overactive thyroid, or hyperthyroidism, can also cause neck pain, hair loss and menstrual and sex-drive problems, as well as insomnia, unexpected weight loss, chronic diarrhea, anxiety and panic attacks, heart palpitations, high blood pressure and bulging eyes.

See their two thyroid related articles here.