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: 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 Pituitary hypothyroidism is a very rare condition where damage to the pituitary gland damages cells that secrete TSH (thyroid stimulating hormone) which stimulates the thyroid to produce normal levels of thyroid hormone

Risk Factors Age (older than 50) Female gender Obesity Thyroid surgery X-ray or radiation treatments to the neck

Early Symptoms 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 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 TSH stimulates the thyroid to produce normal amounts of hormone, TSH secreted by pituitary gland – so damage to pituitary gland causes high TSH (very rare)

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 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.pdf>. "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_hypothyroidism_000038_2.htm>.