What are the other Names for this Condition? (Also known as/Synonyms)

• Hypoactive Thyroid Gland
• Underactive Thyroid
• Underactive Thyroid Gland

What is Hypothyroidism? (Definition/Background Information)

• Hypothyroidism is a condition in which the thyroid gland (present in the neck) is underactive and produces low amounts of the hormone thyroxine, due to a variety of factors. This can result in several symptoms and complications, particularly if it is left undiagnosed and/or untreated
• Thyroxine is responsible for regulating the body's metabolism. It stimulates cells of the body to produce proteins, and also increases the amount of oxygen used by them. It also has a very important role in fetal brain development
• There are two main forms of Hypothyroidism:
  • Primary Hypothyroidism: Hypothyroidism is considered primary when it occurs due to dysfunction of the thyroid gland itself, and not due to factors extrinsic to the gland
  • Secondary Hypothyroidism: In this type, the dysfunction is caused by factors extrinsic to the thyroid gland (i.e., not due to a disorder within the thyroid)
• The cause depends on the type of Hypothyroidism but may include Hashimoto’s thyroiditis, surgical removal of the thyroid gland, pregnancy, radioactive iodine therapy, thyroid gland inflammation, pituitary gland dysfunction, and certain genetic disorders
• The signs and symptoms of Hypothyroidism may include weight gain, irritability, cold intolerance, dry skin, constipation, slow heartbeat, sweating, and fatigue. The associated symptoms of the underlying condition causing secondary Hypothyroidism may also be noted
• Undiagnosed or untreated Hypothyroidism may lead to severe symptoms and complications. The complications may include carpal tunnel syndrome, fluid in the lungs, infertility, pregnancy complications, or poor intellectual development in newborns
• The treatment may involve addressing the symptoms and managing the underlying cause. A replacement of thyroid hormone forms an important part of treating Hypothyroidism. The prognosis is generally good with appropriate early treatment, despite the requirement of medications for a lifetime in some cases

Who gets Hypothyroidism? (Age and Sex Distribution)

• It is reported that about 5% of the global population are affected by Hypothyroidism making it a very common condition worldwide
• The condition may affect both adults and children, including infants
• A large number of cases are diagnosed in women over 60-65 years of age
• Worldwide, all racial and ethnic groups are at risk for Hypothyroidism

According to literature, the prevalence of the condition ranges from 0.2-5.3% and 0.3-3.7% for Europe and USA respectively.

What are the Risk Factors for Hypothyroidism? (Predisposing Factors)

The risk factors for Hypothyroidism may include:

• Postmenopausal women over the age of 60 years have a higher risk for Hypothyroidism
• Positive family history of thyroid disorders
• Having undergone surgery to remove the thyroid gland either totally or partially, for various other health reasons
• Radiation therapy to the head and neck region
• Recent pregnancy
• Autoimmune disorders such as rheumatoid arthritis or Sjögren’s syndrome
• Use of certain medications (drug-induced Hypothyroidism)
• Nutritional deficiency of iodine
• Turner syndrome (genetic disorder)

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Hypothyroidism? (Etiology)

The thyroid gland is a butterfly-shaped gland located in the front of the neck. It is responsible for secreting thyroid hormones that monitor our body temperature, heart rate, blood pressure, and weight. Hypothyroidism is a condition that develops from an underproduction of the thyroid hormones due to various causes.

• This may occur directly due to the dysfunction of the thyroid gland - when its termed primary Hypothyroidism
• Or, it may be due to other health issues in the body that prevent the thyroid gland from secreting enough hormones - termed secondary Hypothyroidism

The cause of Hypothyroidism may broadly include:

• Presence of autoimmune disorders such as Hashimoto’s thyroiditis (most common cause) and atrophic thyroiditis
• Partial or complete thyroidectomy: Due to some health conditions, such as the presence of benign or malignant thyroid tumors, a part or all of the thyroid gland may have to be removed
• Congenital Hypothyroidism: A condition affecting infants that results from a partial or complete loss of thyroid function, due to developmental issues
• Treatment with radioactive iodine (I-131) for various malignancies (such as thyroid cancer or head and neck lymphoma) or Graves’ disease
• Inflammation of thyroid gland (thyroiditis) due infections, certain medications, or pregnancy
• Pituitary gland abnormalities
• Excess or deficient iodine in the body; adequate amounts of iodine in the body regulates the production of thyroid hormone
• Other conditions that affect the thyroid gland and disrupt its normal function, such as amyloidosis, sarcoidosis, and hemochromatosis

What are the Signs and Symptoms of Hypothyroidism?

The signs and symptoms of Hypothyroidism may vary from one individual to another. The rate of development of the signs and symptoms may be slow in many individuals, resulting in a delayed diagnosis of the condition.

The signs and symptoms may include:

• Feeling of tiredness
• Weight gain
• Difficulty in tolerating cold conditions
• Puffed-up face
• Muscle aches and joint pain
• Irregular and heavy menstrual periods
• Constipation or hard stools
• Reduced sweating
• Dryness of skin
• Hair loss
• Goiter or enlarged thyroid gland
• Hoarse voice
• Decreased sense of hearing
• Mental health issues such as depression and absentmindedness
• Abnormally slowed heart rate (slow pulse)
• Shortness of breath
• Myxedema, or swelling of the skin and soft tissues due to the deposition of mucopolysaccharides

Additionally, the signs and symptoms of any associated condition (causing secondary Hypothyroidism) may be noted.

How is Hypothyroidism Diagnosed?

The diagnosis of Hypothyroidism may involve the following tests and procedures:

• Complete evaluation of medical history along with a thorough physical exam
• Assessment of one’s signs and symptoms
• Diagnostic tests for Hypothyroidism may include:
  • TSH blood test
  • T3 and T4 blood test
  • TRH (thyrotropin releasing hormone) blood test
  • Creatine kinase blood test
  • Lipid profile
  • Radioactive iodine uptake test
  • Ultrasound scan of the thyroid gland
  • CT scan of head or MRI of brain to detect tumors in the pituitary gland
• Thyroid gland biopsy, if necessary
• Tests to diagnose an underlying condition may be necessary

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Hypothyroidism?

Complications associated with Hypothyroidism include:

• Myxedema coma: A medical emergency caused by severely deficient levels of thyroid hormones
• Pregnant women are at an increased risk for miscarriage
• High blood pressure during pregnancy or pre-eclampsia
• Infertility
• Fetal death
• Jaundice, poor muscle tone, large-sized head, feeding problems, umbilical hernia, and poor physical and mental development in newborns
• Birth defects in newborn children
• Carpal tunnel syndrome
• Fluid accumulation in the lungs (pleural effusion), around the heart (pericardial effusion), and abdomen (ascites)
• Side effects of thyroxine treatment, including increased risk for hyperthyroidism (due to over-treatment)

Complications that may arise from an underlying or associated health condition may be additionally noted.

How is Hypothyroidism Treated?

The treatment of Hypothyroidism may include:

• Hormone replacement: Administration of thyroid hormone medications (thyroxine) to restore T3, T4, and TSH levels to normalcy
• Symptomatic treatment through medications; bringing about certain lifestyle changes (food, exercise, and stress control)
• Considering early adequate treatment of autoimmune disease, genetic conditions, and infections causing Hypothyroidism
• Treating pituitary gland abnormalities such as pituitary gland tumor removal (if tumor is the cause of thyroid gland function disruption)
• A careful and periodic monitoring of pregnancy (including close fetal monitoring) is advised and recommended

Undertaking treatment of the underlying cause of secondary Hypothyroidism forms an important part of addressing the condition.

Regular medical screening at periodic intervals with tests and physical examinations are necessary, especially for pregnant women.

How can Hypothyroidism be Prevented?

The prevention depends on the risk factors and cause of Hypothyroidism. In many cases, it may not be possible to prevent the condition.

However, considering certain factors may help lower one’s risk for the same: 

• Knowledge about one’s family history is helpful in assessing future risks for the condition
• Drugs that cause the condition may be discontinued or alternative medication prescribed
• Avoiding nutritional (iodine) deficiencies through proper dietary control

Early detection and prompt treatment of causative conditions may lower one’s risk for Hypothyroidism.

What is the Prognosis of Hypothyroidism? (Outcomes/Resolutions)

The prognosis of Hypothyroidism depends on the underlying cause, underlying risk factors, severity of the signs and symptoms, and the response of each individual to treatment measures. In general, the prognosis of Hypothyroidism is good with appropriate treatment.

• Some individuals may either require lifelong medications to keep the symptoms under control; often, a periodic screening of T3, T4, and TSH levels are recommended
• In case of severe symptoms, the prognosis may vary from one individual to another
• The prognosis of secondary Hypothyroidism depends on the severity of the underlying cause associated with it

Additional and Relevant Useful Information for Hypothyroidism:

The following article links will help you understand thyroid-stimulating hormone (TSH), total T3, and total T4 laboratory tests:

http://www.dovemed.com/common-procedures/procedures-laboratory/thyroid-stimulating-hormone-tsh-test/

http://www.dovemed.com/common-procedures/procedures-laboratory/total-t3-blood-test/

http://www.dovemed.com/common-procedures/procedures-laboratory/total-t4-blood-test/