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

• SH (Secondary Hypothyroidism)

What is Secondary 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
• Secondary Hypothyroidism (SH) indicates that the dysfunction is caused by factors extrinsic to the thyroid gland (i.e., not due to a disorder within the thyroid). The cause of the condition may include an abnormally functioning pituitary gland, or the presence of tumors in the brain injuring the pituitary gland
• The signs and symptoms of Secondary 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 Secondary Hypothyroidism may lead to severe symptoms and complications. The complications may include carpal tunnel syndrome, fluid in the lungs, and infertility
• The treatment may involve addressing the symptoms and treating the underlying cause. A replacement of thyroid hormone forms an important part of managing hypothyroidism. The prognosis is generally good with appropriate early treatment, despite the requirement of medications for a lifetime in some cases

Who gets Secondary 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. However, Secondary Hypothyroidism is generally rare
• 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

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

The risk factors for Secondary Hypothyroidism may include:

• Postmenopausal women over the age of 60 years have a higher risk for hypothyroidism
• Head injury
• Brain tumors or cancers
• Chronic stress
• Turner syndrome (genetic disorder)
• Recent pregnancy
• Use of certain medications

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 Secondary 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. Secondary Hypothyroidism is a condition that develops from an underproduction of the thyroid hormones due to other health issues in the body that prevent the thyroid gland from secreting enough hormones.

The cause of Secondary Hypothyroidism may include:

• Pituitary gland and hypothalamus abnormalities
• Presence of benign or malignant brain tumors affecting the pituitary gland and hypothalamus

What are the Signs and Symptoms of Secondary Hypothyroidism?

The signs and symptoms of Secondary 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 Secondary Hypothyroidism Diagnosed?

The diagnosis of Secondary 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
  • 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 and procedures 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 Secondary Hypothyroidism?

Complications associated with Secondary Hypothyroidism include:

• Myxedema coma: A medical emergency caused by severely deficient levels of thyroid hormones
• Infertility
• 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 Secondary Hypothyroidism Treated?

The treatment of Secondary 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)
• Undertaking treatment of the underlying cause of Secondary Hypothyroidism

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

How can Secondary Hypothyroidism be Prevented?

Currently, in many cases, it is not possible to prevent Secondary Hypothyroidism. 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
• Early detection and prompt treatment of causative conditions may lower one’s risk for Secondary Hypothyroidism

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

The prognosis of Secondary Hypothyroidism is generally 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 Secondary 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/