2 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 producedThere are three types of hypothyroidism: primary, secondary, and tertiary
3 Primary Hypothyroidism Due to a defect in the gland, the thyroid cannot make enough T3 and T4The 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 lithiumradiation exposure to the neckradioactive iodine used for treatment of hyperthyroidismspecial x-ray dyessurgical removal of part or all of the thyroid glandsome women develop after pregnancy (postpartum thyroiditis)
4 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 hypothalamusPituitary 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
5 Risk Factors Age (older than 50) Female gender Obesity Thyroid surgery X-ray or radiation treatments to the neck
6 Early Symptoms Cold intolerance Constipation Depression Fatigue WeaknessMuscle or joint painPalenessThin, brittle hair and fingernailsDry, itchy skinWeight gain and water retention
7 Late Symptoms Decreased sense of taste and smell Dry flaky skin HoarsenessMenstrual disordersPuffy face, hands, and feetSlow speechThickening of skinThinning of eyebrows
8 Exams and Tests Physical examination may reveal: Smaller than normal thyroid gland (but sometimes may also be normal in size or enlarged)Coarse facial featuresFirm swelling of arms and legsLoss of the edges of eyebrowsLow blood pressureSlow heart rateLow temperaturePale, yellow, and dry skinSlow muscle relaxation when reflexes are testedThin, brittle hairChest x-ray may show enlarged heart
9 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 T4Total T3 and T4Anemia on a complete blood countIncreased cholesterol levelsIncreased liver enzymesIncreased serum prolactinLow serum sodiumTSH stimulates the thyroid to produce normal amounts of hormone, TSH secreted by pituitary gland – so damage to pituitary gland causes high TSH (very rare)
10 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 usedReceive the lowest dose that relieves symptoms and brings blood tests to a normal rangePeriodic monitoring of TSH levels Requires life-long therapy, can be completely controlled with early treatment
11 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 unresponsivenessDepressionHeart diseaseIncreased risk for infectionInfertilityMiscarriagePituitary tumorsComplications from too much thyroid hormone replacement:Atrial fibrillationOsteoporosisSymptoms of hyperthyroidism
12 ReferencesHolt, Elizabeth H. "Hypothyroidism - primary." Medline Plus N.p., 17 June Web. 4 Dec <http://www.nlm.nih.gov/medlineplus/ency/article/ htm>."Hypothyroidism." American Association of Clinical Endocrinologists N.p., Web. 4 Dec <http://www.aace.com/pub/thyroidbrochures/pdfs/Hypothyroidism.pdf>."Hypothyroidism." Wikipedia N.p., 21 Nov Web. 3 Dec <http://en.wikipedia.org/wiki/Hypothyroidism#cite_ref-nlm_6-0>.Simon, Harvey. "Hypothyroidism." University of Maryland Medical Center N.p., 21 May Web. 4 Dec <http://www.umm.edu/patiented/articles/what_causes_hypothyroidism_000038_2.htm>.
Your consent to our cookies if you continue to use this website.