Overview of Hyperthyroidism
Hyperthyroidism occurs in about 1.2% of Americans. Your thyroid gland produces two iodine-containing hormones – thyroxine (T4) and triiodothyronine (T3). These hormones control how your body uses the fats and carbs you eat, regulate your body temperature, affect your heart rate, and assist in protein production. T3 is much more biologically active than T4.
Hyperthyroidism occurs when the thyroid gland produces too much of the hormone thyroxine, speeding up the metabolism, which might not sound like a bad thing. However, hyperthyroidism can be quite serious, and the symptoms cause misery for those who are untreated. Fortunately, most people respond well to treatment.
Overall, women are two to 10 times more likely than men to develop hyperthyroidism, and the risk increases over the age of 60.
Several chronic illnesses, including type 1 diabetes and primary adrenal insufficiency, increase the risk. One-half of people newly diagnosed with celiac disease also have thyroid disease, and adults with celiac disease have 2.9 times the risk of hyperthyroidism (the risk is 4.8 times higher for children with celiac disease). This article provides more information about the link between celiac disease and thyroid diseases.
Pernicious anemia, caused by a deficiency of vitamin B12, also increases the risk.
Symptoms of Hyperthyroidism
- Unintentional weight loss
- Increased appetite
- Tachycardia (a rapid heartbeat)
- Arrhythmia (a disturbance in the heart’s normal rhythm)
- Anxiety and irritability
- Nervousness and restlessness
- A tremor in the hands and fingers
- Unusual sweating
- Changes in the menstrual cycle
- Heat intolerance
- More frequent bowel movements
- Muscle weakness
- Difficulty sleeping
- Thinning of the skin
- Itchy skin
- Fine, brittle hair and hair loss
- An enlarged thyroid gland (this is called a goiter)
- Rarely, eye problems including dry eyes, red or swollen eyes, excessive tearing, vision changes, and protruding eyeballs can occur. Sometimes individuals with hyperthyroidism appear to be “staring”.
- Nausea and vomiting
- Breast development in men
- Low blood cholesterol and triglycerides
Note that older adults often display different symptoms, such as loss of appetite instead of the usual increase in appetite. Sometimes, older adults become weak, sleepy, confused, withdrawn, and depressed with hyperthyroidism.
Complications of Hyperthyroidism
Unfortunately, untreated hyperthyroidism can be serious and even fatal.
- The heart problems caused by hyperthyroidism, including rapid heart rate, atrial fibrillation (which can cause strokes), and congestive heart failure, are serious complications.
- Untreated hyperthyroidism can cause osteoporosis because the excess thyroid hormones halt the body’s ability to incorporate calcium into the bones.
- Graves’ ophthalmopathy causes bulging, red or swollen eyes, light sensitivity, blurring, or double vision. If left untreated, permanent loss of vision can occur.
- Graves’ dermopathy causes redness and swelling of the skin, usually on the shins and feet.
- Fertility problems in women and complications in pregnancy, including premature birth, low birth weight, high blood pressure, and miscarriage, may occur.
- A thyrotoxic crisis, also know as thyroid storm, is a sudden escalation of symptoms, causing fever, a rapid pulse, systolic hypertension, gastrointestinal distress, and sometimes delirium and seizures. Thyroid storm can progress to coma and the need for mechanical ventilation. This is a life-threatening medical crisis that warrants immediate attention. Thyroid storm can be brought on by stress or infection. Anesthesia can also initiate thyroid storm.
Diagnosis of Hyperthyroidism
Blood tests that measure thyroxine and thyroid-stimulating hormone (TSH) are usually ordered. High levels of T3 and T4 coupled with low levels of TSH indicate an overactive thyroid. Please note that biotin can cause false results on blood tests. Let your doctor know if you are taking any biotin-containing supplements, including multivitamins or “hair and nail” supplements. You’ll need to discontinue taking these supplements at least 12 hours before your blood draw.
A radioactive uptake test requires you to take a small, oral dose of radioactive iodine. Alternatively, the isotope can be injected. At intervals, the amount of radioactive iodine collected in the thyroid gland is measured. A high radioiodine uptake indicates that your thyroid gland produces too much thyroxine, raising suspicion of Graves’ disease or hyperfunctioning thyroid nodules. This test can’t be carried out on pregnant women.
A thyroid scan might be invalidated if you’ve received radiographic contrast agents within the past three months. Medications containing iodine and any thyroid medications will need to be discontinued before the test and you must take nothing by mouth after midnight on the day before the test. This test is contraindicated in pregnancy.
Causes of Hyperthyroidism
Several conditions can cause hyperthyroidism. Graves’ disease, an autoimmune disorder, is the most common cause of hyperthyroidism. In someone with Graves’ disease, the immune system’s antibodies cause the thyroid gland to produce too much T4.
Hyperfunctioning thyroid nodules occur when one or more adenomas (noncancerous lumps) of the thyroid produce too much T4.
The thyroid gland can also become inflamed with certain autoimmune conditions and viral or bacterial infections. Inflammation of the thyroid is called thyroiditis; stored thyroid hormone leaks out of the thyroid gland, causing hyperthyroidism for up to three months. After this period, the thyroid might become underactive (hypothyroidism), which usually lasts for 12 to 18 months but can be permanent.
In 4-7% of women, the thyroid gland malfunctions during the six months following delivery. Those who already had a disorder before becoming pregnant may experience a worsening of the severity. Occasionally, women develop thyroiditis during pregnancy.
Intravenous contrast can cause hyperthyroidism or hypothyroidism. The exact risk is unknown.
Occasionally, someone with hypothyroidism who is overmedicated will develop hyperthyroidism.
Hyperthyroidism is usually treated with anti-thyroid medications and radioactive iodine to slow the production of thyroid hormones. Sometimes, radioactive iodine slows thyroid activity too much, causing hypothyroidism. Side effects of radioactive iodine include dry mouth and eyes, sore throat, and changes in taste.
Anti-thyroid medications include methimazole and propylthiouracil. These drugs usually need to be taken for one to two years. Both of these medications have the potential to cause serious liver disease and can even cause death. They lower resistance to infection by decreasing the number of white blood cells. Anti-thyroid medications can’t be used to treat hyperthyroidism caused by thyroiditis.
Surgery might be the last option for pregnant women and others who can’t tolerate or want radioactive iodine therapy. Risks of thyroid removal include damage to the vocal cords and parathyroid glands. Once the thyroid is removed, lifelong supplementation of thyroid hormone will be necessary. If the parathyroid glands are also removed, medication to keep blood calcium levels normal will also be required.
Bulging of the eyes (exophthalmos) is treated with head elevation, a low-salt diet, artificial tears, and dark glasses. Sometimes, the eyelids will need to be taped closed at night. Diuretics or corticosteroids might be prescribed to reduce swelling.
Beta-blockers can help relieve the symptoms of hyperthyroidism, such as tremor, rapid heart rate, anxiety, and palpitations.
Individuals with hyperthyroidism should avoid consuming foods that are very rich in iodine – most notably seafood such as clams, lobsters, oysters, sardines, and other saltwater fish, as well as seaweed and kelp. Your doctor or dietitian may recommend that you use non-iodized salt.
People with hyperthyroidism typically require 40 calories/kg of body weight. In severe cases, energy needs might be increased by as much as 60%. Because glycogen stores can become depleted, a high carbohydrate diet is warranted. Alcohol might cause hypoglycemia and should be avoided. Avoid caffeine – the last thing someone experiencing trembling and a rapid heart rate needs is additional stimulation.
When people with both hyperthyroidism and celiac disease adopt a gluten-free diet, thyroid antibody levels decrease. It is important for people with both conditions to be scrupulous in maintaining a gluten-free diet.
Roughly 30% of people with thyroid disease experience a vitamin B12 deficiency. Food sources of vitamin B12 include seafood, meat and organ meat, dairy products, fortified cereals, and nutritional yeast.
It’s also important to get enough calcium and vitamin D because hyperthyroidism can contribute to thinning bones.
Fluid needs are also increased and a minimum of 3 liters per day will be required. Fluid loss is sometimes greater from diarrhea, increased respiration, and sweating.
Cough syrups and multivitamins can also contain high amounts of iodine. Additionally, cough syrups and other cold medication may contain stimulants and should also be avoided for this reason. People with hyperthyroidism should talk to a doctor before taking antihistamines or decongestants, which can cause dangerous side effects.
Smoking has been linked to the development of Graves’ ophthalmopathy. If you smoke, talk to your doctor and get help quitting.
A study on patients with Graves’ disease found that those participants enrolled in a structured exercise program had dramatic improvements in subjective measurements of energy and were more likely to discontinue antithyroid medications without relapse. Weight-bearing exercise helps maintain bone density and improve heart health, both of which are especially important for hyperthyroidism.