Hypothyroidism

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Definition/Description

Hypothyroidism is caused by an insufficient amount of the thyroid hormone in the body resulting in an overall slowing of metabolism. There are two categories to classify Hypothyroidism which are primary and secondary.

Prevalence

Hypothyroidism is more prevalent in women who have a four to ten times greater likelihood of developing this than men. Hypothyroidism can be present at birth, but has a higher occurrence rate between the ages of 30 and 60. It occurs in close to 10% of women and 6% of men over the age of 65. Primary Hypothyroidism is more common than secondary with approximately 95% of all people diagnosed categorized as the primary type.

Characteristics/Clinical Presentation

Clinical signs are widespread and affect numerous body systems. With early onset of the disease signs may be indistinct and go undetected such as general fatigue, slight weight gain from fluid retention and decreased metabolism, dry skin, or cold sensitivity. Elderly patients have significantly fewer symptoms than do younger adults, and complaints are often subtle. Many elderly patients with hypothyroidism present with nonspecific geriatric symptoms like confusion, falling, incontinence, and decreased mobility. With progression, clinical signs become more obvious and severe. Myxedema usually appears in the later stages if not treated resulting in nonpitting edema present around the eyes, hands, and feet. Myxedema may also cause thickening of the tongue and tissues of the larynx and pharynx, slurred speech and hoarseness. Rarely, a goiter may be present if not medically treated and presents as a large swelling on the anterior neck resulting from marked thyroid gland growth. Although goiters are not frequently seen in the United States because its main cause is due to low iodine intake it can also be seen in elevated levels of TSH often present in progressed hypothyroidism. It is more commonly seen in other parts of the world where commercial foods containing iodine aren’t as abundant. Other frequent clinical manifestations are listed in the systemic involvement section of this page.

Associated Co-morbidities

Depression
Congestive Heart Failure
Coronary Artery Disease
Peripheral Vascular Disease
Hyperlipidemia
Carpal Tunnel Syndrome
Fibromyalgia
Anemia
Diabetes
Myxedema

Medications

Synthetic hormone replacement therapy is the most common method of treatment for hypothyroidism. Artificial L4 hormone also known as L-thyroxine is used alone or in conjunction with a L3 hormone called liothyronine to supplement the deficient amounts of thyroid hormone that the thyroid is distributing throughout the body. Also, dehydrated animal thyroid hormone L-thyroxine may be used as another preferred method of hormone replacement. The hormone replacement is started at a low dose and then is gradually increased until a proper level is achieved and maintained. This is especially true for the elderly population who may have heart co morbidities because this drug therapy can make the person hyperthyroid for several hours and increases the risk for cardiac events. The dose should be the lowest amount possible to return TSH blood levels close to normal range, although this is not the case for secondary hypothyroidism. L-thyroxine should not be given to someone with secondary hypothyroidism until they begin cortisol hormone therapy first to treat the underlying cause not due to the thyroid gland itself because this drug may hasten adrenal gland emergency.

Diagnostic Tests/Lab Tests/Lab Values

When the body senses that there is a decreased amount of thyroid hormone being produced the anterior pituitary gland increases the amount of thyroid-stimulating hormone (TSH) being release in an effort to promote thyroid hormone production. With Hypothyroidism, the thyroid gland does not respond properly to the TSH so the pituitary gland continues to increase its secretion causing elevated levels of TSH to be present in the blood. 

Elevated TSH levels found in the blood are used most often to diagnose Hypothyroidism because it is the most sensitive indication of the disorder. TSH levels are always elevated in Primary Hypothyroidism. In severe cases T4 hormone levels may be decreased in the blood. T3 levels are typically close to normal in most cases. Cholesterol and triglceride levels may also be elevated.

Causes

 Primary Hypothyroidism is caused by hormone insufficiency related to the loss of productive thyroid tissue or defective hormone production. The most common cause for the development of Primary Hypothyroidism in the United States is autoimmune diseases, in particular, Hashimoto’s Thyroiditis. With this disease the body’s immune system attacks the thyroid gland cells and enzymes in attempt to rid the body of invasion. This destroys the thyroid cells and leaves the gland with little ability to make the thyroid hormone. Primary Hypothyroidism may also be caused by radiation treatment or surgical removal of thyroid. This may be present in people treated for goiters, hyperthyroidism, Hodgkin’s disease, lymphoma, Grave’s disease or cancer of the head, neck, or thyroid gland. Some medicines such as amiodarone, lithium, interferon alpha, and interleukin-2 can prevent the thyroid gland from being able to make the thyroid hormone normally and can be another cause for Primary Hypothyroidism. These drugs usually only cause hypothyroidism in people with a higher genetic disposition to autoimmune diseases. Rarely, primary hypothyroidism is congenital, or present at birth, or caused by deficient iodine intake in the diet. Secondary Hypothyroidism is caused by pathology to the pituitary gland or hypothalamic disease which causes under stimulation to the thyroid gland secondary to inadequate amounts of TSH released to be utilized to make the thyroid hormone.

Systemic Involvement

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Medical Management (current best evidence)

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Physical Therapy Management (current best evidence)

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Alternative/Holistic Management (current best evidence)

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Differential Diagnosis

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Case Reports

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Resources

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Recent Related Research (from Pubmed)

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