Hypothyroidism is the result of insufficient hormone production by the thyroid gland, this butterfly-shaped organ located at the base of the neck, below the Adam’s apple. The people most affected by this condition are women over the age of 50.

The influence of the thyroid gland on the body is major: its role is to regulate the basic metabolism of the cells of our body. It controls energy expenditure, weight, heart rate, muscle energy, mood, concentration, body temperature, digestion, etc. It thus determines the intensity of the energy that makes our cells and organs work. In people with hypothyroidism, this energy works slowly.

At rest, the body consumes energy to keep its vital functions active: blood circulation, brain function, breathing, digestion, and maintaining body temperature. This is called the basal metabolism, which is partly controlled by thyroid hormones. The amount of energy expended varies from person to person depending on the size, weight, age, gender and activity of the thyroid gland.

In the United States, between 4.6 to 9.5% of the population suffer from hypothyroidism, with women 2-8 times more affected than men. The prevalence of the disease increases with age, reaching more than 10% after age.

Congenital or neonatal hypothyroidism

In about 1 in 4,000 babies, hypothyroidism is present from birth, due to a malformation or dysfunction of the thyroid gland. If left untreated, congenital hypothyroidism has serious consequences for a child’s physical and mental development. Fortunately, in the United States, Canada and other developed countries, this disease is systematically detected in all newborns, thanks to a blood test developed in the mid-1970s. This screening allows treatment to be initiated from the first days of life to prevent the consequences of the disease.

Thyroid hormones under control

The 2 main hormones secreted by the thyroid are T3 (triiodothyronine) and T4 (tetra-iodothyronine or thyroxine). Both contend iodine, an essential for their production. The amount of hormones produced is under the control of other glands, located in the brain: the hypothalamus and pituitary. The hypothalamus commands the pituitary gland to produce the hormone TSH (for thyroid stimulating hormone). In turn, the hormone TSH stimulates the thyroid to produce thyroid hormones, including T3 and T4.

An underactive or overactive thyroid gland can be detected by taking a blood test to measure the level of TSH in the blood. TSH levels are high in hypothyroidism because the pituitary gland responds to the lack of thyroid hormones (T3 and T4) by secreting more TSH. In this way, the pituitary gland tries to stimulate the thyroid to make more hormones. In a situation of hyperthyroidism (when there is too much thyroid hormone), the reverse happens: the TSH level is low because the pituitary gland perceives the excess thyroid hormones in the blood and stops stimulating the thyroid gland. Even at the very beginning of a thyroid problem, TSH levels are often abnormal.

Causes of hypothyroidism

Prior to the 1920s, iodine deficiency was the leading cause of hypothyroidism. Iodine is a trace mineral necessary for life and for the production of the thyroid hormones T3 and T4. Since iodine was added to table salt – a practice that began in Michigan in 1924 because of the many cases of hypothyroidism – this deficiency is rare in industrialized countries. However, according to estimates by the World Health Organization, nearly? 2 billion people are still at risk of iodine deficiency12. It remains the number 1 cause of hypothyroidism in the world. In industrialized countries where people are asked to limit salt intake, iodine deficiency may recur.

The main causes of hypothyroidism in industrialized countries today are:

  • Hashimoto’s thyroiditis. This autoimmune disease causes destruction of the thyroid gland by the immune system. Scientists cannot explain what triggers this disease. It would sometimes appear as a result of stress or a viral infection, in people who are predisposed to it.
  • A treatment that alters the thyroid gland. Treatment with radioactive iodine to treat hyperthyroidism or surgery to remove the thyroid gland (due to a nodule, tumor or cancer in the thyroid) leads to permanent hypothyroidism in about 80% of cases. Also, radiotherapy treatment to the neck causes transient hypothyroidism in about 50% of cases, and permanent hypothyroidism in about 25% of cases.
  • Postpartum thyroiditis. In 8 to 10% of women, an autoimmune reaction against the thyroid can occur a few weeks to a few months after childbirth. This is called “postpartum” thyroiditis. In 40% of cases, this thyroiditis leads to hypothyroidism, the symptoms of which are more or less marked. They are most often transient.

Other rarer causes:

  • Certain drugs. Lithium, for example, used for certain psychiatric disorders, or amiodarone (a medicine containing iodine), prescribed for cardiac arrhythmias, can cause hypothyroidism.
  • A congenital anomaly of the thyroid gland, that is, present from birth. Sometimes the gland does not develop normally, or it functions poorly. In this case, hypothyroidism is detected a few days after birth through a routine blood test.
  • A malfunction of the pituitary gland, the gland which regulates the thyroid by the hormone TSH (represents less than 1% of cases).
  • A bacterial or viral infection of the thyroid gland.

Possible complications

Left untreated, the disease can have serious long-term consequences. In adults, myxedema, a severe form of hypothyroidism, can occur. Symptoms of myxedema are a puffy face, yellowing, and dry skin, which appears thickened. In severe cases, certain conditions (infection, cold, trauma, surgery, etc.) can lead to loss of consciousness or a “myxedema” coma. In addition, studies suggest that people who have had hypothyroidism for several years are at greater risk for cardiovascular disease.

In untreated children, significant delays in growth and irreversible intellectual development are observed, commonly called cretinism. Adequate treatment, initiated quickly, usually avoids complications and sequelae.

Symptoms of hypothyroidism are linked to slower metabolism. They depend on the extent of the thyroid hormone deficit and often appear very gradually. Some people have no symptoms; only the blood test can then establish a diagnosis.

Symptoms of hypothyroidism

In adults

  • Lack of energy and fatigue.
  • A reluctance.
  • Unexplained weight gain despite poor appetite.
  • Slowed heart rate which may cause shortness of breath.
  • Irritability and sometimes a depressive state.
  • Cramps, muscle stiffness and pain in the joints.
  • Constipation.
  • The swollen face and eyes.
  • Pale, dry skin.
  • Dry hair, hair loss.
  • Brittle nails.
  • A deeper and hoarse voice.
  • Irregular, longer or even absent menstrual cycles and heavier periods.
  • Infertility.
  • Confusion, difficulty concentrating and memory loss, especially in older people.
  • Goiter (sometimes), which is swelling at the base of the neck caused by the enlargement of the thyroid.
  • High blood cholesterol.

In children at birth (in case of congenital hypothyroidism)

  • Small size at birth, lower than normal with normal or high weight.
  • jaundice (or jaundice, yellowing of the skin) neonatal older than 8 days.
  • Persistence of lanugo (fine hairs of babies at birth)
  • Blue circles around the eyes and nostrils,
  • Widening of the fontanelles.
  • Constipation
  • Lack of appetite, sucking disorders,
  • Big tongue,
  • Abnormally hoarse cries,
  • Muscle hypotonia,
  • Drowsiness,
  • Little crying,
  • Dry skin,
  • Delay of psychomotor acquisitions detectable from the third month.

In older children, the signs resemble those of an adult, with the addition of:

  • Stunted growth,
  • Large muscle volume especially in the calves,
  • Drop in school performance.

People at risk of hypothyroidism

  • Women over the age of 50.
  • People who have a personal or family history of thyroid disease or autoimmune disease (type 1 diabetes, celiac disease, rheumatoid arthritis, etc.).
  • Women who have given birth during the year.

Risk factors of hypothyroidism

  • Smoking while breastfeeding is risky for the baby. A mother’s smoking may decrease the amount of iodine passed into breast milk, which could affect her baby’s thyroid function.
  • Nutritional deficiencies, particularly in iodine, selenium and zinc.
  • Too much iodine. For example, in Japan, where seaweed consumption is high, excess iodine is a common cause of hypothyroidism.
  • Taking certain medicines, such as lithium, amiodarone, or medicines to treat hyperthyroidism. Treatment with radioactive iodine, surgery or radiation therapy to the thyroid are also important risk factors for hypothyroidism.
  • A very abundant consumption of goitrogenic foods. Some foods, when consumed in very large quantities, inhibit the uptake of iodine by the thyroid gland, which prevents the normal production of thyroid hormones. They are called goitrogenic foods because they can eventually cause goiter. Goitrogenic foods are crucifers (Brussels sprouts, cabbage, cauliflower, broccoli, kale, mustard greens, rutabaga, radish, horseradish, etc.), cassava, potatoes sweet, soybeans, peanuts and millet. This situation occurs very rarely in industrialized countries, as people have access to a wide variety of foods. In some parts of Africa, on the other hand, cassava is a staple food. It is considered to be one of the major causes of goiter there. Generally, cooking removes this goitrogenic effect.

Preventing hypothyroidism

Currently, it is not known how to prevent most cases of hypothyroidism that occur in industrialized countries. Even so, early diagnosis and a diet that provides all of the nutrients essential for the proper functioning of the thyroid gland can help prevent symptoms from getting worse and the disease getting worse.

Elsewhere in the world, prevention is possible in cases where nutritional deficiencies (especially in iodine, selenium or zinc), or an excess of iodine, are the cause of hypothyroidism.

Screening measures

A test for congenital hypothyroidism is done in hospitals in all newborns in industrialized countries. TSH hormone levels are measured first, followed by T4 hormone levels in borderline cases. Studies indicate that this early detection can treat the disease quickly and prevent its consequences, such as mental retardation and growth retardation.

In adults, the benefits of screening have not been demonstrated. Therefore, the Canadian and US Preventive Medicine Study Groups do not recommend universal screening. However, several medical associations recommend that the TSH hormone level in the blood be measured periodically in people at risk (taking high-risk medicine or a family history of hypothyroidism) and in those who have symptoms of hypothyroidism.

Basic preventive measures

To produce thyroid hormones, the thyroid needs a sufficient amount of trace elements, especially iodine, selenium and zinc. A deficiency in any of these can slow down the functioning of the thyroid. Iodine deficiency is rather rare in industrialized countries due to the use of iodized table salt. A healthy and varied diet provides all these trace elements. In 2007, according to the World Health Organization, iodine deficiency, although less common than before, remained a public health problem in 47 countries. If in doubt, perform laboratory tests to detect the nutrient deficiency (s).

Here are some good food sources:

  • iodine: sea fish (anchovies, sea bream, mackerel, cod, sardines, etc.), seaweed and table salt.
  • selenium: Brazil nuts, oysters and tuna.
  • zinc: seafood (oysters at the top of the list), beef and veal, beef or pork liver.

Daily iodine requirement: In adults, a daily intake of 150 µg per day is recommended. Requirements are 200 µg per day in pregnant or breastfeeding women. In order not to exceed the recommended daily intake, the World Health Organization recommends consuming a maximum of 5 g of iodized table salt per day, which corresponds to about 1 tsp. of salt per day 13. This amount of salt provides 50 µg to 75 µg of iodine per day.

Measures to prevent aggravation

In people with a problem with the functioning of the thyroid, too much iodine may worsen the disease and interfere with treatment. It is difficult to quantify what constitutes excessive iodine consumption. This depends on the amount of iodine usually consumed and varies greatly from region to region of the world. According to the World Health Organization, consumption of no more than 1000 µg (equivalent to 1 mg) of iodine per day is considered safe.

Several natural products intended for the treatment of thyroid diseases are rich in iodine (tincture of iodine, iodine supplements made from algae, etc.). As a precaution, their use should be reserved for people who have iodine deficiency (which is rare). Consult a physician or health care professional knowledgeable in nutrition before consuming such product.

Take the prescribed treatment daily and consult your doctor regularly to ensure that the dosage of treatment remains correct.

Treatment of hypothyroidism

Hypothyroidism is a disease that cannot be cured, but is very well controlled by taking replacement thyroid hormones daily. The intaking of hormones helps to compensate for poor functioning of the thyroid and to restore normal metabolism.

The most prescribed synthetic hormone is thyroxine (T4) in the form of levothyroxine sodium tablet (Levothyrox®, Novothyral®, Levothyroid® or Synthroid®). Most people will need to take it daily for the rest of their lives. This medication corrects the symptoms of hypothyroidism in adults within a few weeks. In the elderly or those with heart problems, the delay may be longer, as the doses are increased very gradually to protect the heart.

In the body, some of the T4 hormones are converted into triiodothyronine (T3). Therefore, it is usually not necessary to take T3 therapy in addition to levothyroxine. Exceptionally, however, the doctor may prescribe T3 in combination with T4, usually for temporary treatment.

Medical follow-up (including a blood test) usually takes place a few months after starting treatment and then annually or if there are signs of hypo or hyperthyroidism. It makes it possible to verify that the administered dose is still suitable for the body’s needs. Thyroid hormone requirements may vary with age, disease progression, and other factors, such as pregnancy.

If high blood cholesterol is due to hypothyroidism, it usually returns to normal after the hypothyroidism is controlled.

How to take the medication

  • Take the medicine at the same time each day.
  • Always take the medicine in the same way, with or without food, in order to obtain a constant supply of hormones.
  • Avoid taking it with products containing soy milk, since soy decreases the absorption of thyroxine. Water, cow’s milk or orange juice are recommended.
  • It is recommended to wait 4 hours before ingesting the following products, which interfere with the absorption of thyroxine4:
    • products that contain soy;
    • supplements of calcium, iron or antacids which contain calcium or aluminum hydroxide.

In conclusion

Hypothyroidism is often discovered by a routine blood test (TSH test). The disease appears very gradually and its symptoms are easily attributed to all kinds of other causes. It deserves to be treated, however. Unexplained lack of energy and fatigue are constant symptoms to be alerted by. Many people suffer from the effects of hypothyroidism for months before finally seeking medical attention and seeing their lives changed by its simple and highly effective treatment.

Steven Peck

Working as an editor for the Scientific Origin, Steven is a meticulous professional who strives for excellence and user satisfaction. He is highly passionate about technology, having himself gained a bachelor's degree from the University of South Florida in Information Technology. He covers a wide range of subjects for our magazine.