What is hypothyroidism?
The thyroid produces hormones that regulate many different functions in the body, including your heart rate, metabolism, and body temperature. Hypothyroidism is the medical term for an underactive thyroid gland. It means your thyroid can’t produce enough hormones to keep the cells in your body working normally.
Around 5% of Americans over the age of 12, or five people out of every 100, have hypothyroidism. Most cases are mild.
Hypothyroidism develops slowly, and symptoms aren’t always obvious. You may eat a healthy diet and exercise regularly but can’t lose weight. Perhaps you feel tired all the time or struggle to concentrate.
Symptoms of hypothyroidism vary, and may include:
- Weight gain
- A puffy face
- Muscle and joint pain
- Dry skin
- Hair thinning or hair loss
- Heavy or abnormal menstrual periods
- Fertility problems in women
- Slowed heart rate
- Goiter, or an enlarged thyroid, which may cause swelling in your neck. It often leads to swallowing or breathing issues.
Hypothyroidism has many different causes, including:
- Thyroiditis, or inflammation of the thyroid
- Hashimoto’s disease, which is an autoimmune disorder that causes your immune system to attack your thyroid
- Radiation treatment
- Certain medications
- A thyroidectomy, which is a surgical procedure that removes part or all of your thyroid
- Congenital hypothyroidism, a condition you’re born with
- In rare cases, pituitary disease, or an imbalance of iodine in your diet
Who can get it
Certain people are more likely to develop hypothyroidism. You’re at a higher risk if you are:
- A woman
- Age 60 or older
- Have a history of thyroid problems or past thyroid surgery
- Have thyroid issues in your family
- Are pregnant or gave birth in the last six months
- Have medical conditions like rheumatoid arthritis or type 1 diabetes
- Have an iodine deficiency, because the body needs iodine to make thyroid hormone
Diagnosis for hypothyroidism
If you notice any of the symptoms listed above, see your doctor. He or she will take a small sample of blood and send it to a laboratory for analysis. There are several markers, or indicators, of thyroid disease. The most sensitive is called TSH. If your TSH levels are elevated, it means your thyroid isn’t working how it should.
Sometimes, TSH levels are elevated, but not enough to make an accurate diagnosis. If this happens, your doctor may ask you to wait a few weeks then come back for another test. Your blood can also be checked for thyroid antibodies. If these are present in your body, you may have Hashimoto’s thyroiditis.
Treatments for hypothyroidism
The best treatment for hypothyroidism is pure synthetic T4 (levothyroxine sodium). It works just like your thyroid hormone and has few, if any, noticeable side effects. There are several brand name generics available:
All contain the same active ingredient but have different inactive ingredients that can affect how your body absorbs them. It’s best to pick one brand and stick with it. Contact your doctor if your pharmacy switches to a different version. If your hypothyroidism is a permanent condition, you’ll need to take one pill of synthetic T4 a day for the rest of your life.
When you start treatment, the goal is to lower your TSH levels to a midpoint of the normal range and maintain those levels. Your doctor will likely start you on a low dose and check your TSH six to eight weeks later. He or she will then adjust that dose until your TSH reaches the normal range. Once you find the right dose, you’ll have your TSH and T4 levels measured once or twice a year.
There are some specific things you can do to ensure the medication is effective:
- Take the thyroid hormone on an empty stomach
- Don’t skip doses
- For maximum absorption, wait two hours before taking antacids, calcium and iron supplements, or cholesterol medication
Certain prescriptions, like antidepressants, estrogen, or birth control pills, can affect your hormone levels. Your doctor may need to adjust your dose, but it usually remains stable over time. If you’re taking enough T4, it will regulate your TSH levels and ease most symptoms.
Possible complications of hypothyroidism treatments
Thyroxine replacement therapy is generally safe and effective. However, it's important to take the right amount. If your dosage isn't correct it can lead to symptoms of hyperthyroidism, or an overactive thyroid gland. You may notice:
- Fatigue, combined with an inability to sleep
- Feeling more hungry than normal
- Shakiness and nervousness
- Feeling hot when others are cold
- Shortness of breath
- Rapid heartbeat
If you notice these symptoms, make an appointment with your doctor and have your TSH tested. If the levels are low, it’s an indication of too much thyroid hormone, and you’ll need a smaller amount.
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American Thyroid Association: "Hypothyroidism (Underactive)."
Harvard Medical School: "Treating hypothyroidism."
Johns Hopkins Medicine: "Hypothyroidism."
National Institutes of Health: "Hypothyroidism (Underactive Thyroid)."
NYU Langone Health: "Diagnosis Hypothyroidism in Adults."