When your thyroid gland is overactive (hyperthyroidism) and produces too much hormone, your body’s metabolism speeds up. Considering the whole-body effects this can have, a variety of symptoms may result, including weight loss, irritability, irregular heart rhythm, tremor, insomnia, hair loss, and more. Hyperthyroidism also carries some potential complications with it, such as bone weakening, atrial fibrillation, and pregnancy concerns, though these are more common when the disease goes untreated or uncontrolled.

Frequent Symptoms

Most people with hyperthyroidism experience one or more of the following symptoms. While these symptoms typically come on gradually, they may begin abruptly, especially in young people. On the other hand, older people with hyperthyroidism tend to have fewer and less noticeable symptoms than younger people. 

As you can see, hyperthyroidism can affect the entire body, top to bottom:

Temperature

Increased sweating, as the body produces more heat, is another common symptom of hyperthyroidism. This excess sweating is linked to heat intolerance, which means a person may have a hard time tolerating a warm environment or activities that further increase heat production, like exercise.

Skin/Hair/Nails

In addition to thinning hair and a softening of the nails, the skin of a person with hyperthyroidism is often unusually smooth and warm, due to a rise in blood flow.

Heart

Due to increased pumping of the heart, a person with hyperthyroidism will often notice their heart racing or pounding. Irregular heart rhythms (called arrhythmias) and high blood pressure may also occur with an overactive thyroid gland.

Lung

Shortness of breath, especially with exercise, is common in older people with hyperthyroidism. It occurs as a result of a weakness of their breathing muscles, as well as an increased demand for oxygen within the body.

Intestines 

Digestive symptoms, like dyspepsia and frequent bowel movements/diarrhea, may occur in hyperthyroidism as a result of the increase in gut motility.

Weight loss, despite an increase in appetite, is due to both the increase in gut mobility (which leads to fat malabsorption) and metabolic rate (which means the body is burning through calories quicker than normal). While this increase in metabolism may initially energize people, eventually they become fatigued as the body tires out.

Neck

An enlargement of the thyroid gland (called a goiter) may occur in some people with hyperthyroidism, causing potential symptoms like a sore throat and/or neck discomfort. Neck swelling may become noticeable, especially when a person tries to put on a tie or scarf. A goiter may eventually cause problems swallowing or even breathing.

Urinary Tract

Urinating more often, during the daytime and nighttime, is common in people with hyperthyroidism.

Reproductive System

Due to an alteration of sex hormones in the body, women with hyperthyroidism may develop infrequent menstrual periods. With severe hyperthyroidism, a woman may stop menstruating (amenorrhea).

Since the excess thyroid hormone converts testosterone to estradiol (a type of estrogen), men may experience a decrease in their sex drive, erectile dysfunction, and swelling of their breast tissue (gynecomastia). In addition, sperm production is often reduced or abnormal.

Brain and Nerves

A tremor of the hands often occurs in hyperthyroidism, along with behavioral and personality changes, such as depression, anxiety, nervousness, and/or irritability. Insomnia, as well as difficulties with concentrating or remembering things, are also frequently reported in hyperthyroidism.

Complications

There are a few major complications that may result from having hyperthyroidism, especially if left untreated.

Other Symptoms to Look For

Other medical problems, like anemia (a decrease in red blood cells) and abnormal liver function tests, can be the first clue that a person has an overactive thyroid.

Eye 

Some people develop eye issues (called Graves’ ophthalmopathy), which may cause gritty, red eyes or protrusion of the eyes due to swelling behind the eyeballs. In severe cases, double vision can develop.

Bone

Hyperthyroidism is linked to osteoporosis, which causes bone weakening, making a person more prone to breaking bones with even minor bumps or falls.

In hyperthyroidism, there is a high risk of developing atrial fibrillation, especially in older people. Atrial fibrillation is a common heart arrhythmia that can lead to serious problems like stroke or heart failure.

Thyroid Storm

Thyroid storm is a rare but very serious, potentially life-threatening condition that occurs in people with untreated hyperthyroidism. It may also be triggered by a stressful event like surgery, trauma, or infection.

Thyroid storm is characterized by exaggerated symptoms of hyperthyroidism, such as a very fast heart rate, high fever, diarrhea, agitation, delirium, and/or decreased consciousness.

Pregnancy

While mild hyperthyroidism in pregnancy does not usually cause problems for a mother and her baby, moderate-to-severe hyperthyroidism in a mother can lead to various complications. 

For the baby, according to the American Thyroid Association, uncontrolled or untreated hyperthyroidism of the mother during pregnancy is associated with size that is small for gestational age, preterm birth, stillbirth, and possibly congenital malformations. 

For the mother, potential complications of untreated hyperthyroidism include pre-eclampsia and, rarely, thyroid storm. 

Fetal Neonatal Hyperthyroidism

For a pregnant woman with Graves’ disease (the most common cause of hyperthyroidism in pregnancy), there is a small risk that her baby will develop hyperthyroidism before birth (called fetal thyrotoxicosis) or be born with hyperthyroidism (called neonatal hyperthyroidism). 

Some babies are born hyperthyroid while others take days or weeks (up to three) to develop hyperthyroidism. Neonatal Graves’ disease, the most common cause of hyperthyroidism in newborns, occurs when the mother passes the thyroid-stimulating antibodies to her child, causing the baby to have a temporary case of hyperthyroidism.

If your baby develops hyperthyroidism, some symptoms may include: 

While uncommon, hyperthyroidism may also occur in the newborns of mothers who have a history of treated Graves’ disease (meaning their disease is in remission). This is why it’s important to notify your healthcare provider of any history of thyroid disease, in addition to active thyroid disease.

  • Low birth weightAn unusually small head circumference (microcephaly)Warm, moist skinIrritability and poor sleepFast heartbeatA dangerous accumulation of fluid, known as fetal hydrops (rare)

When to See a Healthcare Provider

If you are concerned you (or a loved one) is experiencing one or more symptoms of an overactive thyroid gland, be sure to see your healthcare provider for a proper evaluation. The good news is that your thyroid function can be easily checked with a simple blood test, called the thyroid-stimulating hormone (TSH) test. 

Lastly, if you are taking antithyroid medications for hyperthyroidism and considering pregnancy, it’s important to seek guidance from your general practitioner and, perhaps, an endocrinologist. You want to be sure your thyroid function is well controlled prior to and during pregnancy.

Of course, seek medical attention right away if you notice alarming symptoms, like an irregular pulse, problems breathing, or delirium.

Frequently Asked Questions

  • What are the symptoms of hyperthyroidism?
  • Symptoms of hyperthyroidism (overactive thyroid gland) can vary from person to person and may include:FatigueMuscle weaknessNervousness or irritabilityInsomniaMood swingsHeat intoleranceTremorsDiarrhea or frequent loose stoolsWeight lossIrregular heartbeatIrregular periodsBrittle hairGoiter (an enlarged thyroid gland)
  • Why are hyperthyroidism symptoms worse at night?
  • Sleep difficulty, night sweats, restless legs syndrome (RLS), and nighttime urination are common in people with hyperthyroidism. During sleep, a rise in thyroid hormones—which regulate energy use and body temperature—can trigger these and other nighttime symptoms.
  • What are the symptoms of congenital hyperthyroidism?
  • Congenital hyperthyroidism is usually caused by Graves disease in the mother. Symptoms in a newborn include irritability, rapid heartbeat, rapid breathing, excessive appetite, and poor weight gain. The baby may also have exophthalmos (bulging eyes) and goiter like the mother.
  • What are the possible complications of hyperthyroidism?
  • Impaired fertility is a common complication due to irregular periods. Hyperthyroidism can also cause atrial fibrillation (increasing the risk of stroke and heart failure), osteoporosis, and a thyrotoxic crisis (a potentially life-threatening condition triggered by the excessive release of thyroid hormones).
  • Can you have symptoms of hyperthyroidism with normal thyroid tests?
  • Yes. Typically, the thyroid hormones T3 (triiodothyronine) and T4 (thyroxine) will be high in people with hyperthyroidism. Subclinical hyperthyroidism occurs when TSH (thyroid stimulating hormone) levels are low but T3 and T4 are normal. Even so, subclinical hyperthyroidism may cause symptoms and can even lead to overt hyperthyroidism if left untreated.
  • How do symptoms of hypothyroidism and hyperthyroidism differ?
  • Hypothyroidism (low thyroid function) can cause many of the same symptoms as hyperthyroidism, including fatigue, irregular periods, and goiter. But it is more likely to cause weight gain than weight loss, cold sensitivity instead of heat sensitivity, and constipation rather than diarrhea. Only an investigation by a healthcare provider can confirm whether you have thyroid disease and the type involved.

Symptoms of hyperthyroidism (overactive thyroid gland) can vary from person to person and may include:

Sleep difficulty, night sweats, restless legs syndrome (RLS), and nighttime urination are common in people with hyperthyroidism. During sleep, a rise in thyroid hormones—which regulate energy use and body temperature—can trigger these and other nighttime symptoms.

Congenital hyperthyroidism is usually caused by Graves disease in the mother. Symptoms in a newborn include irritability, rapid heartbeat, rapid breathing, excessive appetite, and poor weight gain. The baby may also have exophthalmos (bulging eyes) and goiter like the mother.

Impaired fertility is a common complication due to irregular periods. Hyperthyroidism can also cause atrial fibrillation (increasing the risk of stroke and heart failure), osteoporosis, and a thyrotoxic crisis (a potentially life-threatening condition triggered by the excessive release of thyroid hormones).

Yes. Typically, the thyroid hormones T3 (triiodothyronine) and T4 (thyroxine) will be high in people with hyperthyroidism. Subclinical hyperthyroidism occurs when TSH (thyroid stimulating hormone) levels are low but T3 and T4 are normal. Even so, subclinical hyperthyroidism may cause symptoms and can even lead to overt hyperthyroidism if left untreated.

Hypothyroidism (low thyroid function) can cause many of the same symptoms as hyperthyroidism, including fatigue, irregular periods, and goiter. But it is more likely to cause weight gain than weight loss, cold sensitivity instead of heat sensitivity, and constipation rather than diarrhea. Only an investigation by a healthcare provider can confirm whether you have thyroid disease and the type involved.