Hypothyroidism is when the thyroid gland does not produce enough thyroid hormones to meet the needs of the body.
The thyroid is underactive.
The opposite is hyperthyroidism, where the thyroid produces too much thyroid hormone. However, the link between hyperthyroidism and hypothyroidism is complex, and one can lead to the other, in certain circumstances.
Thyroid hormones regulate metabolism or the way the body uses energy. If thyroxine levels are low, many of the body’s functions slow down.
About 4.6 percent of the population aged 12 years and above in the United States has hypothyroidism.
The thyroid gland is found in the front of the neck below the larynx, or voice box, and has two lobes, one on each side of the windpipe.
It is an endocrine gland, made up of special cells that make hormones. Hormones are chemical messengers that relay information to the organs and tissues of the body, controlling processes such as metabolism, growth, and mood.
The production of thyroid hormones is regulated by thyroid-stimulating hormone (TSH), which is made by the pituitary gland.
This, in turn, is regulated by the hypothalamus, a region of the brain. TSH ensures that enough thyroid hormones are made to meet the needs of the body.
- Fast facts on hypothyroidism
- The thyroid gland produces two thyroid hormones, TS3 and TS4.
- These hormones regulate the body’s metabolism.
- The most common cause of hypothyroidism in the U.S. is Hashimoto’s disease.
- Symptoms of hypothyroidism include fatigue, cold intolerance, and joint and muscle pain.
Symptoms
Hypothyroidism refers to the underproduction of hormones in the thyroid gland. It has a wide range of symptoms.
Thyroid hormones affect multiple organ systems, so the symptoms of hypothyroidism are wide-ranging and diverse.
The thyroid creates two thyroid hormones, triiodothyronine (T3) and thyroxine (T4). These regulate metabolism, and they also affect the following functions:
- brain development;
- breathing;
- heart and nervous system functions;
- body temperature;
- muscle strength;
- skin dryness;
- menstrual cycles;
- weight;
- cholesterol levels.
Symptoms of hypothyroidism commonly include, but are not limited to:
- fatigue;
- weight gain;
- cold intolerance;
- slowed heart rate, movements, and speech;
- joint and muscle pain, cramps, and weakness;
- constipation;
- dry skin;
- thin, brittle hair or fingernails;
- decreased sweating;
- pins and needles;
- heavy periods, or menorrhagia;
- weakness;
- high cholesterol;
- puffy face, feet, and hands;
- insomnia;
- balance and coordination issues;
- loss of libido;
- recurrent urinary and respiratory tract infections;
- anemia;
- depression.
If left untreated, the following symptoms can manifest:
- hoarseness;
- puffiness in the face;
- thinned or missing eyebrows;
- slow heart rate;
- hearing loss.
If it develops in children or teenagers, the signs and symptoms are generally the same as adults.
However, they may also experience:
- poor growth;
- delayed development of teeth;
- poor mental development;
- delayed puberty.
Hypothyroidism develops slowly. Symptoms may go unnoticed for a long time, and they may be vague and general.
Symptoms vary a great deal between individuals, and they are shared by other conditions. The only way to obtain a concrete diagnosis is through a blood test.
Causes
Hypothyroidism can occur if the thyroid gland fails to work properly, or if the thyroid gland is not stimulated properly by the hypothalamus or pituitary gland.
Hashimoto’s thyroiditis
The most common cause of hypothyroidism in the U.S. is Hashimoto’s thyroiditis, also known as chronic lymphocytic thyroiditis or autoimmune thyroiditis.
Hashimoto’s thyroiditis is an autoimmune disease, a disorder in which the immune system attacks the body’s own cells and organs.
The condition causes the immune system to attack the thyroid gland, leading to inflammation and interfering with its ability to produced thyroid hormones.
Thyroiditis
Thyroiditis is an inflammation of the thyroid gland. It causes thyroid hormones to leak into the blood, raising their overall levels and leading to hyperthyroidism. After 1 to 2 months, this may develop into hypothyroidism.
Thyroiditis can be caused by viral or bacterial infection, an autoimmune condition, or following pregnancy.
Congenital hypothyroidism
In cases of congenital hypothyroidism, the thyroid gland does not function properly from birth.
This can lead to physical and mental growth problems, but early treatment can prevent these complications. Most newborns in the U.S. are screened for hypothyroidism.
- Thyroid surgery and treatment as causes of hypothyroidism
- Hypothyroidism can occur after part of the thyroid is removed during surgery.
- Thyroid treatment and surgery can lead to hypothyroidism.
Several conditions such as hyperthyroidism, goiters, thyroid nodules, and thyroid cancer can be treated by partially or fully removing the thyroid gland. This may result in hypothyroidism.
Radiation treatment of the thyroid can also lead to hypothyroidism. Radioactive iodine is a common treatment for hyperthyroidism. It works by destroying the cells of the thyroid gland and decreasing the production of T4.
Radiation is also used to treat people with head and neck cancers, Hodgkin’s disease, and other lymphomas, which can lead to damage of the thyroid gland.
Medication
A number of drugs can interfere with thyroid hormone production. These include amiodarone, interferon-alpha, interleukin-2, lithium, and tyrosine kinase inhibitors.
Pituitary gland abnormalities
If the pituitary gland stops functioning properly, the thyroid gland may not produce the correct amount of thyroid hormone.
Pituitary tumors or pituitary surgery can affect the function of the pituitary gland, and this can adversely affect the thyroid gland.
Sheehan’s syndrome is a condition that involves damage to the pituitary gland.
If a woman loses a life-threatening amount of blood or has severely low blood pressure during or after childbirth, the gland can be damaged, causing it to under-produce pituitary hormones.
Iodine imbalance
Iodine is needed for the production of thyroid hormones, but the level must be balanced. Too much or too little iodine can lead to hypothyroidism or hyperthyroidism.
Treatment
Treatment for hypothyroidism focuses on supplementing the thyroid hormone. At present, doctors cannot cure hypothyroidism but they can help people to control it in most cases.
Synthetic thyroxine
To replenish levels, doctors usually prescribe synthetic thyroxine, a medication that is identical to the T4 hormone. Doctors may recommend taking this in the morning before eating each day.
Dosage is determined by the patient’s history, symptoms, and current TSH level. Doctors will regularly monitor the patient’s blood to determine if the dosage of synthetic T4 needs to be adjusted.
Regular monitoring will be required, but the frequency of blood tests will likely decrease over time.
Iodine and nutrition
Iodine is an essential mineral for thyroid function. Iodine deficiency is one of the most common causes of goiter development or abnormal enlargement of the thyroid gland.
Maintaining adequate iodine intake is important for most people, but those with autoimmune thyroid disease can be particularly sensitive to the effects of iodine, meaning that it can trigger or worsen hypothyroidism.
They should inform their doctor if they are sensitive to the effects of iodine.
People with hypothyroidism should discuss any major dietary changes with their doctor, especially when starting a high fiber diet, or eating lots of soy or cruciferous vegetables.
Diet can affect the way in which the body absorbs thyroid medication.
During pregnancy, iodine requirements increase. Using iodized salt in the diet and taking prenatal vitamins can maintain the required levels of iodine.
Iodine supplements are available for purchase online.
Hypothyroidism can normally be managed appropriately by following the advice of a qualified healthcare practitioner. With appropriate treatment, thyroid hormone levels should return to normal.
In most cases, medications for hypothyroidism will need to be taken for the rest of the patient’s life.
Prevention
There is no way to prevent hypothyroidism, but people who may have a higher risk of thyroid problems, for example, women during pregnancy, should check with their doctor about the need for additional iodine.
Screening is not recommended for those who do not have symptoms unless they have the following risk factors:
- a history of autoimmune disease;
- previous radiation treatment to the head or neck;
- a goiter;
- family history of thyroid problems;
- use of medications known to affect thyroid function.
These people can be tested for early signs of the condition. If tests are positive, they can take measures to prevent the disease from progressing.
There is no evidence that a particular diet will prevent hypothyroidism, and there is no way to prevent hypothyroidism unless you live in a region with low iodine levels in the diet, for example, some parts of Southeast Asia and Africa.
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