Thyroid gland, Underactive Thyroid, Hypothyroidism

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Thyroid gland, Underactive Thyroid, Hypothyroidism


Hypothyroidism (hypo: meaning low) or Underactive thyroid is a condition in which thyroid gland is not able to produce enough thyroid hormone. The insufficient secretion of thyroid hormone causes many body functions to slow down.

Thyroid glands are part of endocrine system. The specialized doctor who treat these patients are called endocrinologist.

Thyroid glandThe thyroid gland is located below the voice box (larynx) in the front part of the neck.  It is recognized as butterfly shaped gland of approximately 2 inch in length.  There are two lobes of thyroid – one on each side and they are connected by the isthmus (a piece of tissue).

The thyroid gland mainly secretes two hormones:

1. Triiodothyronine (T3)

2. Thyroxine (T4)

Primarily, T3 hormone is made from T4. The T3 is more active hormone than T4 and it directly acts on the tissues. These hormones are secreted in the blood and travel to all parts of the body affecting almost all organs.

The main function of thyroid hormone is to regulate body functions - the way energy is utilized by body. This process is referred as metabolism.

The production and release of thyroid hormone is controlled by another hormone called Thyroid-stimulating hormone (TSH) produced by pituitary gland located at the base of the brain.

Thyroid hormones need iodine to work properly. Iodine is usually available in the diet such as in iodized salt and naturally in many fruits and vegetables.

Underactive thyroid is a common condition, which is very difficult to prevent.

Hypothyroidism can occur both in men and women, however more common in women. About 10-15 out of 1000 women have hypothyroidism whereas 1 out 1000 men suffers with hypothyroidism.

The good news is that the most underactive thyroid cases can be easily treated with effective and safe medication. 

Hypothyroidism Affecting Women

Women who are especially older than 60 years are more likely to have underactive thyroid.  It upsets normal balance of chemical reactions in the body.  This condition seldom causes symptoms in early stages, but if left untreated, it could cause various health related problems like joint pain, heart disease, obesity and infertility in women.

Some women develop hypothyroidism during or after pregnancy because they produce antibodies, which attack their own thyroid gland (Hashimoto’s disease). If this condition is not treated immediately, it could affect the health of mother, baby or both. It could also increase the risk of miscarriage, premature delivery or increase in blood pressure of the mother. Moreover, developmental malformations could occur in the developing baby.

Since symptoms develop gradually, many patients do not notice any problem in the beginning.  Symptoms may become worse if left untreated.

Some of the symptoms are listed below

  • Feeling tired or fatigued
  • Puffy or swollen face
  • Unexpected weight gain
  • Goiter (swollen thyroid gland affecting breathing and swallowing)
  • Dry, pale skin
  • Constipation
  • Increased sensitivity to cold
  • Hoarse voice
  • Fertility problems in women
  • Pain, swelling or stiffness in joints
  • Tenderness, cramps or muscle ache
  • Depression
  • Heavier menstrual period in women
  • Forgetfulness
  • Thin and brittle fingernails and hair
  • Visibly large thyroid gland

Hypothyroidism may occur due to various causes, some of the common causes are

Hashimoto’s Disease (HD)

HD is the most common cause of hypothyroidism. It’s an auto-immune disease caused when antibodies attacks the person’s own thyroid gland tissues. As a result, the thyroid gland tissues are damaged and production of thyroid hormone is reduced.

Inflammation of thyroid or Thyroiditis

In early stages, inflammation of thyroid gland causes leakage of thyroid hormone in the blood resulting in overactive thyroid (hyperthyroidism).  After few months, those patients suffer with reduced thyroid hormone (hypothyroidism). This hypothyroidism would remain for about 1- 2 years or in some people it affects for life-long.

Hypothyroidism due to thyroid gland inflammation could occur because of

Postpartum thyroiditis – that is developed in women after childbirth

Subacute thyroiditis – painful condition, the cause is unknown, but usually occurs after some infection

Thyroid Surgery - Removing all or a large portion of thyroid gland during a thyroid surgery could also decrease or stop hormone production.

Radiation Therapy -  Radiation therapy to treat cancers of the neck and head may affect thyroid gland and lead to hypothyroidism.

Pituitary Disorder -  Thyroid stimulating hormone is produced by pituitary gland, this hormone tells the thyroid gland how much thyroid hormone to produce. If any disorder occurs in the pituitary gland, it is not able to produce right amount of thyroid stimulating hormone and that leads to hypothyroidism.

Deficiency of Iodine -  Iodine is a mineral utilized by our body to make thyroid hormones. When deficiency of iodine occurs, thyroid gland is not able to produce enough thyroid hormone.

Congenital Disease - Some babies are born with either absence of thyroid gland or defective thyroid gland. Such babies have congenital hypothyroidism.

Some medicines may also cause hypothyroidism

Risk Factors

Following are the risk factors that increase the chances of developing hypothyroidism

 - Being a women (women are 2-10 more likely to develop hypothyroidism than men)
 - Family history of thyroid disease such as goiter
 - Older than 60 years
 - Radioactive iodine or anti thyroid medications
 - Autoimmune diseases, such as lupus, pernicious anemia, rheumatoid arthritis and type 1 diabetes
 - Radiation received to the upper chest or neck
 - Pregnancy or delivered baby in the last 6 months
 - Any previous thyroid surgery

The doctor will perform clinical examination and ask questions to understand the medical and family history of the patient.

Blood tests to measure hormone levels helps in confirming the diagnosis.

Thyroid function test looks at the levels of thyroxine (T4) and thyroid stimulating hormone (TSH) in the blood. T4 test measures the actual amount of circulating thyroid hormone in the blood. In underactive thyroid, T4 level in blood is lower than the normal.

If there is high level of TSH and a low level of T4 in blood that means the person’s thyroid gland is underactive. If the test result shows raised TSH but normal T4, the person may be at risk of developing an underactive thyroid in the future.

Blood tests are also used for other measurements, such as checking the level of a hormone called triiodothyronine, but this is not a routine test.

Thyroid autoantibody test is done to look for the presence of thyroid antibodies. Many people with Hashimoto’s disease have these antibodies.

An underactive thyroid is usually treated by taking daily hormone replacement tablets which are called levothyroxine. It is a synthetic thyroid hormone taken daily in the form of a tablet. This drug replaces thyroxine hormone, which is not produced by thyroid gland in an adequate quantity.

Levothyroxine is considered as a very safe, effective and affordable drug that would very much control the condition for most hypothyroid patients. The patients should continue taking the medication regularly as per doctor’s instruction.

Levothyroxine is started on low dose and then gradually the dose is increased, depending on how the body responds. It requires a few months while dose is adjusted to the patients.

Combination therapy is used in some parts of the world, using levothyroxine and triiodothyronine together.  It is not used routinely because levothyroxine has better effects when it is used alone.

If not treated, hypothyroidism could lead to following complications

Goiter -  Underactive thyroid could cause enlargement of thyroid gland creating a swollen lump in the neck termed as goiter. This lump makes swallowing difficult and can also affect the appearance.
Mental Health Issues: Depression could occur with hypothyroidism and can become worse over time.
High Cholesterol (Increased risk of Heart Disease): An underactive thyroid causes high levels of bad cholesterol (LDL).

Myxedema - It is a rare, life-threatening condition which is characterized by drowsiness followed by severe sluggishness, intense sensitivity to cold, leading to come or unconsciousness.
Pregnancy Complication: If hypothyroidism is not treated during pregnancy, it could lead to following problems

  • Anemia in the mother
  • Pre-eclampsia: It is a condition which causes high blood pressure and fluid retention in the mother and developmental problems in the baby
  • Birth defects
  • Bleeding after birth
  • Underactive thyroid in baby
  • Stillbirth or miscarriage
  • Low birth weight or premature baby
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