The thyroid is a relatively small gland located in the lower neck, which produces the hormone thyroxine. Thyroxine regulates many aspects of the body’s metabolism – mainly the rate at which the body metabolizes nutrients and oxygen and produces energy. Changes in the thyroid’s output can cause either hyperthyroidism or hypothyroidism, both of which affect critical body functions.

When the thyroid gland is not functioning correctly

The thyroid gland’s most common malfunctions are to over-produce or under-produce hormones known as T3 (triiodothyronine) and T4 (thyroxine or tetraiodothyronine). 

An over-functioning thyroid gland can trigger hyperthyroidism – sometimes called thyrotoxicosis or overactive thyroid. The most common cause of hyperthyroidism in the U.S. is Graves’ disease, an autoimmune disorder. Doctors may prescribe Methimazole, or suggest surgical removal or treatment with radioactive iodine.

An under-functioning thyroid may lead to hypothyroidism. It frequently stems from Hashimoto’s Disease, which is also an autoimmune disorder. Drugs like Synthroid and Cytomel can be prescribed that boost the levels of the thyroid hormone thyroxine. 

More than twelve percent of the U.S. population will experience hyperthyroidism or hypothyroidism at some point in their lives, according to the American Thyroid Association (ATA). Women are far more likely than men to have thyroid problems, especially following pregnancy and menopause. A family history of either Hashimoto’s or Graves’ Disease can significantly increase the probability of some thyroid malfunction (see more below).

Undiagnosed thyroid disease may put patients at risk for certain serious conditions, such as cardiovascular diseases, osteoporosis, and infertility. Pregnant women with undiagnosed or inadequately treated hypothyroidism have an increased risk of miscarriage, preterm delivery, and severe developmental problems in their children.

Most thyroid diseases are life-long conditions that can be managed with proper and timely medical attention.

Causes of overactive thyroids and hyperthyroidism.

The most common causes of hyperthyroidism are:

• Graves’ disease, in which the immune system mistakenly identifies a part of the body, in this case, the thyroid gland, as a threat and targets it. In Graves’ disease, specific antibodies called thyroid-stimulating immunoglobulins (TSIs) are produced. TSIs mimic the action of thyroid-stimulating hormone (TSH), normally produced by the pituitary gland, to regulate thyroid hormone production. By binding to the thyroid cells, TSIs continuously stimulate the gland, leading to an excess of thyroid hormones being released into the bloodstream. This disruption in the standard feedback loop between the pituitary gland and the thyroid gland results in an elevation of thyroid hormone levels, causing the symptoms associated with hyperthyroidism. 
• Toxic nodular goiter, in which nodules or lumps in the thyroid gland produce excessive amounts of thyroid hormones.
• Thyroiditis, or thyroid gland inflammation, can be caused by various viral infections, autoimmune conditions, or in mothers after childbirth.
• Excessive iodine intake, either through diet or medications, can lead to hyperthyroidism in susceptible individuals.
• Medications such as amiodarone (used for heart rhythm disorders) or interferon-alpha (used in treating certain cancers and viral infections) can induce hyperthyroidism.

Causes of underactive thyroids and hypothyroidism

The most common causes of hypothyroidism are:

• Hashimoto’s thyroiditis (or Hashimoto’s disease), which is a disorder in which the immune system attacks and damages the thyroid gland, decreasing thyroid hormone production.
• Iodine deficiency. Iodine is a crucial dietary substance required for thyroid hormone synthesis. Sources of iodine include iodized table salt, seafood, seaweed, and vegetables. Decreased iodine intake can cause iodine deficiency and decrease thyroid hormone synthesis.
• Surgical removal of the thyroid gland or treatment with radioactive iodine for patients with thyroid cancer (thyroidectomy or radioactive iodine treatment) will result in hypothyroidism.
• Certain medications, such as lithium (which treats bipolar disorder) and amiodarone (used for heart rhythm disorders), can interfere with thyroid hormone production and contribute to hypothyroidism.
• Congenital hypothyroidism: Some individuals are born with an underactive thyroid gland, which can be due to genetic factors or during the development of a fetus’s thyroid gland while in the womb. The thyroid gland begins to form early in pregnancy, and any disruption or impairment in this process can affect its function. The developing fetus relies on the mother’s thyroid hormones for proper growth and development, especially early on when the fetal thyroid gland is not fully functional. If anything interferes with the normal development of the fetal thyroid gland, it can lead to congenital hypothyroidism, where the baby is born with an underactive thyroid gland. Factors contributing to developmental issues during pregnancy include genetics, maternal thyroid disorders (such as untreated or poorly controlled hypothyroidism in the mother), exposure to certain medications or substances, maternal iodine deficiency, or if the mother has Hashimoto’s disease.
• Age-related thyroid decline occurs as individuals age, particularly in older adults. 

Thyroid cancer

As people age, they become increasingly likely to develop thyroid nodules, which are solid or fluid-filled lumps inside the thyroid gland. The nodules can grow large enough to impede breathing or swallowing. In most cases, the nodules are harmless and produce no symptoms. Unusually large cells in the gland may be an indeterminant precursor of cancer, and in about 25%-30% of the cases do go on to be found to be cancerous.

Thyroid problems in children

Thyroid problems are often associated with adults, but statistics show that thyroid disorders are the most frequent endocrine illnesses reported among school-age children. Symptoms of thyroid disorders that parents should watch out for in children include:

• Excessive fatigue
• Intolerance to exercise
• Slow response time
• Dry, coarse, and sparse hair
• Thickened, dry, and coarse skin
• Slow speaking and hoarse voice
• Sagging eyelids
• Cramps and increased menstrual flow in girls and young women.

Symptoms of hyperthyroidism or hypothyroidism.

The main symptoms of hyperthyroidism can be goiter, mood swings and hair loss. Other milder effects are:

• Weight loss
• Anxiety, nervousness or irritability
• Muscle weakness causing hand tremors
• Heat sensitivity
• Frequent or loose bowel movements.

The main symptoms of hypothyroidism are:

• Fatigue
• Weight gain
• Depression
• Constipation
• Heavy or irregular menstrual periods, or problems in conceiving. 

FAQ

What thyroid symptoms should you be aware of?

When doctors suspect that the thyroid may be overactive, the most frequent physical signs are goiter (swelling of the thyroid gland) or lumps inside the gland, causing difficulties with breathing or swallowing, or patients complaining of one or more of the main symptoms. The diagnosis would typically be confirmed by blood tests that detect a high T4 (thyroxine) and a low TSH (thyroid-stimulating hormone).

What are some silent thyroid symptoms to look out for?

Hyperthyroidism can cause a wide range of symptoms. Doctors watch out for signs of mood swings, depression, nervousness, anxiety and irritability; sleeping problems resulting in persistent tiredness and weakness; extreme sensitivity to heat; goiter; heart palpitations; joint and muscle pain; dry skin or dry, thinning hair. There can be heavy or irregular menstrual periods and fertility problems in women.

What is the number 1 cause of hyperthyroidism?

Graves’ disease is the most frequent cause of hyperthyroidism. It is an autoimmune disorder where the immune system attacks the thyroid and causes it to over-produce the hormone.

What is a thyroid symptoms test?

Blood tests for hyperthyroidism measure the thyroid hormones T4 and T3 as well as TSH.  When TSH is low and T4 and T3 levels are high, this will indicate hyperthyroidism.

What happens if you ignore hyperthyroidism or hypothyroidism?

If hyperthyroidism or hypothyroidism is left treated, it can lead to multiple health problems. Palpitations (an irregular heartbeat) can result in cardiac problems such as blood clots, stroke, or heart failure. Persistently high levels of thyroid hormones can lead to Graves’ ophthalmopathy, which can cause light sensitivity, double vision, and pain.

Can too much kelp cause hyperthyroidism?

Nutritional deficiencies are one of the leading causes of thyroid disorders. The thyroid gland is nutrient-dependent, especially requiring the intake of iodine-rich foodstuffs. A diet that is high in processed foods, especially sugars and fats, and low in the required vitamins and minerals, may lead to lower thyroid hormone output.