The thyroid is an essential endocrine gland in your body. It controls and regulates how your body burns energy, makes proteins, and how sensitive it should be to certain hormones. It constitutes the central energetic of your body. The thyroid gland, located in the front of the neck just below the larynx, secretes hormones that control metabolism. These hormones are thyroxine (T4) and triiodothyronine (T3. However, sometimes, the thyroid fails to work efficiently. One of the medical conditions that can cause this disorder is hypothyroidism, also called underactive thyroid.
What is Hypothyroidism?
Hypothyroidism, commonly called underactive thyroid, is a common medical condition in which your thyroid gland produces inadequate hormones, triiodothyronine (T3) and thyroxine (T4). Secretion of these hormones is regulated by a pituitary hormone called thyrotropin (or thyroid-stimulating hormone). Thyrotropin is secreted by a gland located on the underside of your brain, the hypophysis (pituitary gland). These hormones (T3 and T4), essential to your health, are involved in many functions of your body such as bone growth, mental development, oxygen consumption, metabolism of sugar and dietary fats.
Underactive Thyroid Causes and Risk Factors
Although Hypothyroid can occur in anyone regardless of gender or age, it is more common in elderly and females in their middle age. Hypothyroidism causes are multiple and vary from one person to another. The primary cause is malfunction in the thyroid gland itself. Underactive thyroid can also be resulted of malfunctioning of the pituitary gland due to other factors making the thyroid unable to produce enough thyroid – stimulating hormone (TSH). In very rare cases, hypothyroidism can be linked to a peripheral resistance to hormones T3 and T4.
Autoimmune disease – the most common cause of underactive thyroid is Hashimoto thyroiditis, a pathological condition characterized by an increased volume of the thyroid gland due to abnormal attacks of the immune system to destroy the gland. This chronic inflammation of the thyroid is more common among women 30 to 40 years. The evidence of the disease is possible by researching antithyroglobulin antibodies and antithyroperoxidase antibodies, which are found in thyroid cells. Those antibodies can indicate not only the presence of autoimmune thyroid disease (Hashimoto’s thyroiditis), but also thyrotoxicosis, systemic lupus erythematosus (SLE), thyroid cancer, Grave’s disease, and Type 1 diabetes.
Hyperthyroidism medications – prolonged treatment for hyperthyroidism such as radioactive iodine or anti-thyroid medications can impair the hormonal production of your thyroid gland. Although rare, hyperthyroidism treatment can lead to an irreversible underactive thyroid.
Cancer Treatment – cancer therapies such as radiation used in the treatment of head or neck cancer can damage your thyroid function. The radiation can cause permanent hypothyroidism in some patients.
Thyroid surgery – partial or total surgical removal of the thyroid gland due to certain diseases such as tumor or thyroid cancer can decrease or stop its hormonal production.
Congenital disease – although rare, hypothyroidism can be the result of a congenital abnormality. In this condition, the thyroid gland is underdeveloped, which makes its hormone production inadequate. The disorder is found mostly in infants born of a mother who heavily smokes cigarette.
Diet – Iodine deficiency can increase the volume of the thyroid gland and causes goiter (thyroid goiter), a swelling in the base of your neck just below your Adam’s apple or larynx. Because of abundance of iodized salt (table salt is rich in iodine), this condition is however rare in developed countries.
Pregnancy – after pregnancy, some women develop of form of hypothyroidism called postpartum hypothyroidism. This condition may also occur during pregnancy; it is then more serious, and able to affect the development of the fetus. In addition, postpartum hypothyroidism can cause miscarriage or premature delivery.
Who are at risk of hypothyroidism?
Although hypothyroidism can affect anyone, it is shown to be more frequent in the following groups:
- Women aged over 50 years
- Children born from a cigarette smoker mother
- Individual who have personal or family history of thyroid disease
- People who have autoimmune disease such as type 1 diabetes, celiac disease
- People who have a lack of iodine, selenium, and zinc in their diet
- Those who take certain medications such as lithium and amiodarone against psychiatric disorders and heart problems.
Underactive Thyroid Symptoms
Depending on the seriousness of the disease, you may have hypothyroidism for years without present any obvious symptoms. When symptoms finally occur, the severity tends to vary from one patient to another. Besides mental disorders (nervousness, anxiety, confusion) hypothyroidism can be characterized particularly by lack of appetite, chronic fatigue, muscle weakness, constipation, intolerance to cold, dry and rough skin, hoarse voice, and brittle hair. The symptoms may vary from mild to severe. The most severe form is called myxedema coma, a loss of brain function due to chronic hypothyroidism.
Other signs of hypothyroidism can include:
- Weight gain
- Swelling at the base of your neck (goiter)
- High levels of blood cholesterol
- Abnormal menstrual periods (irregular and more abundant)
- Muscle cramps and stiffness
- Growth problems (children)
- Slow heart beat
- Swollen face
- Thyroid cancer (very rare)
- Lack of dynamism
- Need to spend many hours of sleep
- Depressive tendencies
How hypothyroidism is diagnosed?
In general, a blood test called TSH test is done to diagnose hyperthyroidism. However, blood test alone is not accurate enough to highlight hypothyroidism; the test can reveal signs of hypothyroidism in normal blood. The diagnosis is often supplemented with other exams.
CT scan, ultrasound of the thyroid gland and dosage of antithyroid antibodies can also be used to confirm the diagnosis.
In case of Hashimoto thyroiditis, antigens can be used to target the antithyroglobulin, antithyroperoxidase and antireceptor antibodies. Antithyroperoxidase antibodies are originated of a transformation of iodine by the thyroid. The origin of antithyroglobulin antibodies is not well known to scientists. Antireceptor antibodies of HRT are rarely the cause of hypothyroidism and barely found in the diagnosis.
Underactive Thyroid Treatment
The treatment is intended to replace the deficiency of the thyroid hormones. Levothyroxine (Levoxyl, Synthroid) is the most common medication used in the treatment of underactive thyroid disease. Depending on your health, in less than two weeks, the drug can provide a noticeable relief from symptoms of fatigue, high cholesterol levels, weight gain, etc. However, the treatment must be continued even when symptoms apparently disappear. In addition, your thyroid hormone levels should be monitored yearly after a stable dose of medication is determined. Although rare, in some people adverse effects may include:
- Increased appetite
- Increased heart beat
- Abnormal menstruation
- Abdominal cramps
- Weight loss
- Heat intolerance or excessive sweating
Those side effects can be prevented or reversed when taking the medication with a healthy diet accompanied with regular exercise. Healthy supplements can help your body to better absorb the synthetic thyroid hormone.
Why it is necessary to treat hypothyroidism?
If left untreated, hypothyroidism can lead to major health problems such as:
- Cardiovascular disease
- Miscarriage or birth defects
- Mental disorder (depression, stress, etc.)
- Myxedema coma, a rare, but severe form of hypothyroidism complication.
References: New England Journal of Medicine, Familial Forms of Thyroid Dysgenesis among Infants with Congenital Hypothyroidism, Volume 343:441-442