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Chiefs Morning Report April 10, 2012

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Case Presentation A 50-years-old woman presented to the ED with chest pain and dyspnea. On the day of admission she collapsed and was unresponsive for a short while. She had not suffered from any episodes of syncope before. PMH: single kidney; no h/o DM or HTN Physical examination revealed a well nourished woman with a blood pressure of 90/60 mmHg and a pulse rate of 100 beats per minutes. She had a puffy face and examination of the neck revealed no struma (a swelling in the neck due to an enlarged thyroid gland). The jugular venous pressure was normal. Cardiac auscultation was normal and the lungs were clear. Peripheral pulses of radial, femoral and dorsalis pedis were present. ECG was done and is shown.

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She received magnesium and was transferred to the CCU.

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Next ECG obtained from the patient revealed T wave inversion and prolongation of QT intervals of 0.71 S. The patient received phenytoin as treatment for prolongation of QT intervals. At the third day of admission the patient developed positional vertigo and her blood pressure dropped to 80mmHg. Diagnostic laboratories were drawn.

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Thyroid function test revealed Total T 4 0.71 g/dL, free T 4 (FT4) 0.1 ng/mL, total T 3 74 g/dL and thyroid stimulating hormone 36 U/mL. Other laboratory data such as blood urea nitrogen (BUN), Creatinine and electrolytes were in normal range. The patient received levothyroxine 100 g/day. Two months after treatment with levothyroxine, QT intervals normalized and ventricular tachycardia was abolished. Her periorbital edema had diminished and both TSH and free T4 had normalized.

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HYPOTHYROIDISM

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Objectives Identify Risk Factors for hypothyroidism Discuss clinical presentation, signs and symptoms of hypothyroidism Diagnose and distinguish primary, secondary and tertiary hypothyroidism Discuss treatment of hypothyroidism

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Risk Factors Personal history Previous thyroid dysfunction Goiter Surgery or radiotherapy affecting the thyroid gland DM Vitiligo Pernicious anemia Leukotrichia (premature gray hair) Medications and other compounds Family history Thyroid disease Pernicious anemia DM Primary adrenal insufficiency

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Clinical Presentation Symptoms and signs of the disease vary in relation to the magnitude of the thyroid hormone deficiency and acuteness with which the deficiency develops May be modified by factors such as coexisting nonthyroidal illness Hypothyroidism caused by hypothalamic-pituitary disease may have associated endocrine deficiencies masking the manifestations of hypothyroidism Hypothyroidism after treatment of Graves' hyperthyroidism, some manifestations may persist throughout the patient's life 5-8x more likely in women

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Many of the manifestations of hypothyroidism reflect one of two changes induced by lack of thyroid hormone 1.A generalized slowing of metabolic processes. This can lead to abnormalities such as fatigue, slow movement and slow speech, cold intolerance, constipation, weight gain, delayed relaxation of deep tendon reflexes, and bradycardia. 2.Accumulation of matrix glycosaminoglycans in the interstitial spaces of many tissues This can lead to coarse hair and skin, puffy facies, enlargement of the tongue, and hoarseness. These changes are often more easily recognized in young patients, and they may be attributed to aging in older patients.

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Common Signs and Symptoms of Thyroid Dysfunction Hypothyroidism Fatigue Weight gain Cold intolerance Skin dryness Hair dryness or loss Depression Dementia Muscle cramps and myalgias Edema Bradycardia Constipation Menstrual irregularity (especially menorrhagia) Infertility Hyperthyroidism Fatigue Weight loss Heat intolerance Hyperhydrosis Nervousness Insomnia Tremor Muscle weakness Dyspnea Palpitations Tachycardia and atrial tachyarrhythmias Hyperdefecation Menstrual irregularity (especially hypomenorrhea)

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Pretibial Myxedema

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DIAGNOSIS Primary vs. Secondary or Tertiary Hypothyroidism

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Major causes of hypothyroidism Primary hypothyroidism: Chronic autoimmune thyroiditis Iatrogenic Thyroidectomy, radioiodine therapy or radiation Iodine deficiency or excess Drugs Thionamides, lithium, amiodarone, INF Infiltrative diseases Transient hypothyroidism Painless thyroiditis, postpartum, Congenital thyroid agenesis, dysgenesis, or defects in hormone synthesis Central hypothyroidism TSH deficiency TRH deficiency Pituitary mass lesions Radiation Surgery Infiltrative disorders Sarcoid, TB, hemochromatosis, syphilis, fungal infections Generalized thyroid hormone resistance

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UpToDate

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Primary Hypothyroidism 95% of cases of hypothyroidism Caused by disease of the thyroid gland with decreased secretion of thyroxine (T4) and triiodothyronine (T3) -> reduction in the serum concentrations of the two hormones -> compensatory increase in TSH secretion Characterized by a high serum TSH concentration and a low serum free T4 concentration

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Forms of primary hypothyroidism Subclinical hypothyroidism high serum TSH concentration in the presence of normal serum free T4 and T3 concentrations few if any symptoms and signs of hypothyroidism Overt hypothyroidism high serum TSH concentration in the presence of a low serum free T4 concentration symptoms and signs of hypothyroidism

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Hashimotos thyroiditis Chronic autoimmune (Hashimoto's) thyroiditis Cell- and antibody-mediated destruction of thyroid tissue: 1.Cytotoxic T cells may directly destroy thyroid cells. 2.More than 90 percent of patients have high serum concentrations of autoantibodies to thyroglobulin, thyroid peroxidase, or the thyroid Na/I transporter

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Nuclear accidents and thyroid French prophylaxis: In an individual with a healthy thyroid, taking 100 mg of stable iodine immediately before exposure to radioactive iodine reduces the dose to the thyroid by at least 95% Distribute iodine around nuclear sites Chernobyl Accident: The 26 April 1986 accident at the Chernobyl nuclear power plant contaminated large areas of northern Ukraine as well as parts of Belarus and the Russian Federation. The environmental fallout included radionuclides of iodine, primarily iodine-131 ( 131 I), which concentrates in the thyroid gland increased prevalence of thyroid cancer and subclinical hypothyroidism significant relationship between prevalence of hypothyroidism and individual 131 I thyroid doses due to environmental exposure

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Central Hypothyroidism (Secondary and Tertiary) Insufficient stimulation of the thyroid gland by TSH, by either hypothalamic (tertiary) or pituitary (secondary) disease Low serum T4 concentration and a serum TSH concentration not appropriately elevated Suspect when: Known hypothalamic or pituitary disease Pituitary mass lesion is present Symptoms and signs of hypothyroidism associated with other hormonal deficiencies