Reviewed by:  Dr. Robert Cooper, M.D., FACE

Thyroid disease can be bad enough by itself, but left untreated it can lead to even more serious conditions. Whether the diagnosis is a tendency to produce too much thyroid hormone (hyperthyroidism) or too little (hypothyroidism), the earlier you find out, the better your chances of preventing some of these complications:

• Obesity. Thyroid hormones regulate metabolism, so when the thyroid isn’t producing enough (hypothyroidism), you may experience rapid weigh gain: Your metabolism has significantly slowed down.
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• Heart disease. Both hypothyroidism and hyperthyroidism can damage your heart. Hypothyroidism can lead to high levels of LDL (“bad”) cholesterol and an enlarged heart. If you have hyperthyroidism you may experience a rapid pulse and an irregular heart rhythm. Both conditions can lead to heart failure.
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• Infertility and birth defects. Hypothyroidism can make it difficult to conceive, and risky to have a baby. Too few thyroid hormones can decrease your fertility or cause a miscarriage during pregnancy. Even if you carry your baby to full term, untreated thyroid disease may result in birth defects, such as neurological or developmental problems.
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• Brittle bones. Hyperthyroidism (too much thyroid hormone) can lead to osteoporosis and an increased risk of bone fractures.
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• Eye disease. Certain types of hyperthyroidism, such as the autoimmune condition Graves’ disease, can lead to swelling around the eyes, causing bulging eyes and difficulty closing the eyes. That can lead to double vision, cornea scarring and, in some cases, vision loss.
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• Skin and muscle disease. Hyperthyroidism can also lead to muscular weakness, fatigue and changes to the skin. In severe cases, the muscles may even begin to break down, leading to partial or periodic paralysis.
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• Thyrotoxic crisis. In severe cases, hyperthyroidism can lead to thyrotoxic crisis, or thyroid storm, which causes your symptoms to suddenly intensify. You may experience high fever, a very rapid pulse or delirium. It can lead to a coma.

The good news: If you begin treating your thyroid disease before it worsens, you can prevent these complications.

What's Next: Signs of an Underactive Thyroid

• 10 Signs of an Overactive Thyroid
• Get Your Thyroid Tested
• Lifestyle Tips for a Healthy Thyroid
• Check Your Neck
• Ask Your Doctor About Hypothyroidism
• Ask Your Doctor About Hyperthyroidism

Review Date: November 19, 2008