Hypothyroidism
Randi Schutz
The Thyroid
• Gland that regulates metabolism
• Located in the front of the neck
just below the voice box (larynx)
• The thyroid gland releases two
hormones: thyroxine (T4) and
triioxdothyronine (T3)
• The thyroid gland, as well as the
pituitary gland and hypothalamus,
control how much of these
hormones are produced
• There are three types of
hypothyroidism: primary,
secondary, and tertiary
Primary Hypothyroidism
• Due to a defect in the gland, the thyroid cannot make
enough T3 and T4
• The most common cause of primary hypothyroidism in
the United States is the destruction of the thyroid gland
by the immune system (Hashimoto’s thyroiditis)
• Other causes of primary hypothyroidism include:
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certain drugs such as lithium
radiation exposure to the neck
radioactive iodine used for treatment of hyperthyroidism
special x-ray dyes
surgical removal of part or all of the thyroid gland
some women develop after pregnancy (postpartum thyroiditis)
Secondary & Tertiary
Hypothyroidism
• In secondary hypothyroidism the thyroid gland produces too little
hormone due to disorders of the pituitary gland (i.e. pituitary
hypothyroidism)
• Tertiary hypothyroidism is caused by disorders of the hypothalamus
Risk Factors
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Age (older than 50)
Female gender
Obesity
Thyroid surgery
X-ray or radiation treatments to the neck
Early Symptoms
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Cold intolerance
Constipation
Depression
Fatigue
Weakness
Muscle or joint pain
Paleness
Thin, brittle hair and fingernails
Dry, itchy skin
Weight gain and water retention
Late Symptoms
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Decreased sense of taste and smell
Dry flaky skin
Hoarseness
Menstrual disorders
Puffy face, hands, and feet
Slow speech
Thickening of skin
Thinning of eyebrows
Exams and Tests
• Physical examination may reveal:
– Smaller than normal thyroid gland (but sometimes may also be
normal in size or enlarged)
– Coarse facial features
– Firm swelling of arms and legs
– Loss of the edges of eyebrows
– Low blood pressure
– Slow heart rate
– Low temperature
– Pale, yellow, and dry skin
– Slow muscle relaxation when reflexes are tested
– Thin, brittle hair
• Chest x-ray may show enlarged heart
More Exams and Tests
• Laboratory tests include:
– High levels of thyroid stimulating hormone (TSH)
indicate that the thyroid is not producing sufficient
levels of thyroid hormone (mainly T4). TSH does not
diagnose secondary and tertiary hypothyroidism.
– Low free T3 and T4
– Total T3 and T4
– Anemia on a complete blood count
– Increased cholesterol levels
– Increased liver enzymes
– Increased serum prolactin
– Low serum sodium
Treatment
• Treatment is to replace the thyroid
hormone that is lacking
– T4 is used most often, but a combination of
T4 and T3 is also used
– Receive the lowest dose that relieves
symptoms and brings blood tests to a normal
range
• Periodic monitoring of TSH levels
Requires life-long therapy, can be
completely controlled with early treatment
Related Complications
• Myxedema coma, the most severe from of hypothyroidism (rare)
– Signs and symptoms include: low temperature, decreased breathing,
low blood pressure, low blood sugar, and unresponsiveness
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Depression
Heart disease
Increased risk for infection
Infertility
Miscarriage
Pituitary tumors
Complications from too much thyroid hormone replacement:
– Atrial fibrillation
– Osteoporosis
– Symptoms of hyperthyroidism
References
Holt, Elizabeth H. "Hypothyroidism - primary." Medline Plus N.p., 17
June 2008. Web. 4 Dec. 2009.
<http://www.nlm.nih.gov/medlineplus/ency/article/000367.htm>.
"Hypothyroidism." American Association of Clinical Endocrinologists
N.p., 2006. Web. 4 Dec. 2009.
<http://www.aace.com/pub/thyroidbrochures/pdfs/Hypothyroidism.pd
f>.
"Hypothyroidism." Wikipedia N.p., 21 Nov. 2009. Web. 3 Dec. 2009.
<http://en.wikipedia.org/wiki/Hypothyroidism#cite_ref-nlm_6-0>.
Simon, Harvey. "Hypothyroidism." University of Maryland Medical
Center N.p., 21 May 2009. Web. 4 Dec. 2009.
<http://www.umm.edu/patiented/articles/what_causes_hypothyroidis
m_000038_2.htm>.