Hyperthyroidism vs. Hypothyroidism: Signs and Symptoms

by Sarah Carpenter

Hyperthyroidism and hypothyroidism sound similar phonetically, but they’re actually very different. For example, hyperthyroidism can cause you to lose weight and hypothyroidism can cause you to gain it. In case you’re confused, we’ll define each, explain common characteristics and symptoms and learn about the different treatment options to help you on your journey toward better health.

Hyperthyroidism vs. Hypothyroidism

The difference between hyperthyroidism and hypothyroidism is quantity. Someone with hyperthyroidism has a thyroid that makes too much thyroid hormone. Hyperthyroidism involves higher levels of thyroid hormones which makes your metabolism speed up. On the flip side, someone with hypothyroidism has a thyroid that makes very little thyroid hormone. If you have hypothyroidism, your metabolism slows down. Let’s take a deeper look.

What Is Hyperthyroidism?

The term hyperthyroidism refers to any condition in which there is too much thyroid hormone produced in the body. In other words, the thyroid gland is overactive. Another term that you might hear for this problem is thyrotoxicosis which refers to high thyroid hormone levels in the bloodstream, irrespective of their source.

Symptoms of Hyperthyroidism

The thyroid hormone plays a significant role in the pace of many processes in the body, known as your metabolism. If there is too much thyroid hormone, every function of the body tends to speed up. Some of the symptoms of hyperthyroidism are nervousness, irritability, increased sweating, a racing heart, hand tremors, anxiety, difficulty sleeping, thinning of your skin, fine brittle hair and weakness in your muscles — especially in the upper arms and thighs. You may have more frequent bowel movements. You may lose weight in spite of a good appetite and, for women, menstrual flow may lighten and menstrual periods may occur less frequently.

Since hyperthyroidism increases your metabolism, many individuals initially have a lot of energy. However, as hyperthyroidism continues, the body tends to break down, and this makes being tired very common. Hyperthyroidism can present differently in older adults than it does in young adults. It’s sometimes mistaken for depression or dementia, and they might experience loss of appetite or withdrawal from people.

Causes of Hyperthyroidism

Hyperthyroidism has several causes including:

  • Graves’ disease
  • Overactive thyroid nodules
  • Inflammation of the thyroid gland (called thyroiditis)
  • Too much iodine
  • Too much thyroid hormone medicine
  • A noncancerous tumor of the pituitary gland

Treatment for Hyperthyroidism

Several treatments for hyperthyroidism exist. The best approach for you depends on your age, physical condition, the underlying cause of hyperthyroidism, personal preference and the severity of the disorder. Possible treatments include:

  • Radioactive iodine: Taken by mouth, radioactive iodine is absorbed by your thyroid gland where it causes the gland to shrink. Symptoms usually subside within several months. Excess radioactive iodine disappears from the body in weeks to months.
  • Anti-thyroid medications: These medications gradually reduce symptoms of hyperthyroidism by preventing your thyroid gland from producing excess amounts of hormones. They include methimazole (Tapazole) and propylthiouracil. Symptoms usually begin to improve within several weeks to months, but treatment with antithyroid medications typically continues for at least a year and often longer.
  • Beta blockers: Although these drugs are typically used to treat high blood pressure and don’t affect thyroid levels, they can ease symptoms of hyperthyroidism such as tremors, a rapid heart rate and palpitations. For that reason, your doctor may prescribe them to help you feel better until your thyroid levels are closer to normal.
  • Surgery (thyroidectomy): In a thyroidectomy, your doctor removes most of your thyroid gland. Risks of this surgery include damage to your vocal cords and parathyroid glands — four tiny glands situated on the back of your thyroid gland that help control the level of calcium in your blood. In addition, you’ll need lifelong treatment with levothyroxine (Levoxyl, Synthroid and others) to supply your body with normal amounts of thyroid hormone. If your parathyroid glands also are removed, you’ll need medication to keep your blood-calcium levels normal.

What Is Hypothyroidism?

Hypothyroidism is also a kind of thyroid disease. If you have hypothyroidism that means you have an underactive thyroid — it does not make enough thyroid hormone to keep the body running normally. Low thyroid hormone levels cause the body’s functions to slow down.

Symptoms of Hypothyroidism

Hypothyroidism has a variety of symptoms. You may notice that you feel colder. You get tired more easily. Your skin is getting drier. You are becoming forgetful and depressed, and you are getting constipated.

Symptoms of hypothyroidism usually appear slowly over several months or years. However, some people develop symptoms of hypothyroidism quickly over a few months. In general, the lower your thyroid hormone levels become and the longer they stay low, the more severe your symptoms will be. The only way to know for sure if you have hypothyroidism is through blood tests because the symptoms are so variable.

Causes of Hypothyroidism

Hypothyroidism has several causes including:

  • Hashimoto’s disease
  • Thyroiditis (inflammation of the thyroid)
  • Congenital hypothyroidism — or hypothyroidism that is present at birth
  • Surgical removal of part or all of the thyroid
  • Radiation treatment of the thyroid
  • Some heart, bipolar disorder and cancer medicines
  • Too much or too little iodine in the diet
  • Disorders of the pituitary gland or hypothalamus in the brain

Treatment for Hypothyroidism

Hypothyroidism is treated by replacing the hormones that your own thyroid can no longer make. You will take levothyroxine — a thyroid hormone medicine identical to a hormone a healthy thyroid makes. Usually prescribed in pill form, this medicine is also available as a liquid and as a soft gel capsule. These newer formulas may help people with digestive problems to absorb the thyroid hormone. Your doctor may recommend taking the medicine in the morning before eating.

Your doctor will give you a blood test about 6 to 8 weeks after you begin taking the medicine and could adjust your dose if needed. Each time your dose is adjusted, you’ll have another blood test. Once you’ve reached a dose that’s working for you, your doctor will probably repeat the blood test in 6 months, and then once a year after that.

Hypothyroidism most likely can be completely controlled with thyroid hormone medicine, as long as you take the recommended dose as instructed. Never stop taking your medicine without talking with your doctor first. Taking too much thyroid hormone medication can cause serious problems such as atrial fibrillation or osteoporosis.


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Sarah Carpenter is a freelance writer whose portfolio spans the industries of healthcare, higher education and entertainment. Find out more at her website.


American Thyroid Association – Hyperthyroidism (Overactive)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) – Hyperthyroidism (Overactive Thyroid)
Mayo Clinic – Hyperthyroidism (Overactive Thyroid)
Cleveland Clinic – Hypothyroidism