Your thyroid gland is all about energy. It regulates your metabolism. It affects your bones, your heart and your muscles. It has an impact on everything and it uses hormones to do it.

If you have an overactive thyroid gland, or hyperthyroidism, your thyroid is overproducing hormones. This can make you sweat and feel overheated. It can make your heart beat very fast, and make it hard to keep weight on.

If you have an underactive thyroid gland, or hypothyroidism, you're not producing enough hormones to enable your body to get things done. You feel tired and weak.

If you are a woman in midlife, you may think you are dealing with symptoms of menopause but there might be something amiss with your thyroid instead. There are similarities between many symptoms of menopause and hypothroidism.

"If you are experiencing symptoms of menopause and the symptoms persist despite appropriate therapy, ask your doctor to do a thyroid screen (TSH). A blood sample is all that is needed to make the initial diagnosis of hypothyroidism and treatment is easily achieved with thyroid replacement therapy."

http://health.webmd.com/cgi-bin21/DM/y/nBFn70O8s2S0F80B2yS0EL