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Clinical Application Hypothyroidism and Hyperthyroidism. Gail Nunlee-Bland, M.D. Hypothyroidism. Clinical condition associated with decreased function of the thyroid gland and a decrease in the circulating level of thyroid hormones. Hypothyroidism Causes. Three categories
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Clinical ApplicationHypothyroidism and Hyperthyroidism Gail Nunlee-Bland, M.D.
Hypothyroidism • Clinical condition associated with decreased function of the thyroid gland and a decrease in the circulating level of thyroid hormones
HypothyroidismCauses • Three categories • permanent loss or atrophy of thyroid tissue (primary hypothyroidism) • compensatory thyroid enlargement due to transient or progressive impairment of hormone biosynthesis (goitrous hypothyroidism) • insufficient stimulation of a normal gland as a result of hypothalamic or pituitary disease (secondary hypothyroidism)
Primary Atrophic Hypothyroidism • Autoimmune thyroiditis (Hashimoto’s disease) • Postablative I 131 or surgery • Athyreotic due to ageneisis or dysplasia • Unresponsivenes to TSH
Goitrous Hypothryoidism • Hashimoto’s thyroiditis • Endemic iodine deficiency • Iodine-induced • Antithyroid agents
Central Hypothyroidism • Secondary (pituitary) hypothyroidism • Panhypopituitarism • Isolated TSH deficiency • Abnormal TSH synthesis or receptor defect • Hypothalamic hypothyroidism
Autoimmune Thyroiditis • More common in women • Thyroid autoantibodies present • autoantibodies to thyroid peroxidase (TPOAB) • autoantibodies to thyroglobulin (TgAb) • May be associated with other autoimmune diseases
Postablative Hypothyroidism • Common cause of thyroid failure in the adult • Follows total thyroidectomy secondary to thyroid cancer or subtotal thyroidectomy for Graves’ disease • Following treatment with radioactive iodine
Athyreotic Hypothyroidism • Development defects of the thyroid • Incidence 1 in every 4000 newborns • Defects • complete absence • failure of thyroid to descend properly during embryologic development
Hashimoto’s Thyroiditis • Most common cause of goitrous hypothyroidism in iodine sufficient areas • Autoimmune
Endemic Goiter • Environmental iodine deficiency • Affects more than 200 million people throughout the world • Most common in mountainous areas - Alps, Himalayas, and Andes • Consumption of cassava meal may aggravate
Antithyroid Agents • Lithium • Para-aminosalicylic acid • Phenylbutazone • Topically applied resorcinol • ethionamide • Soybean in infant formulas
Iodine-induced • Chronic administration of large doses of iodine • may be seen when potassium iodide, radiographic contrast medium, or amiodarone • May occur in newborns when women given large quantities of iodine during pregnancy
Central Hypothyroidism • Due to hypothalamic or pituitary disease • May be associated with other pituitary hormone deficiencies • May precipitate adrenal crises if thyroid hormone is replaced before hydrocortisone
Cardiovascular • Cardiac output is decreased • Peripheral vascular resistance is increased • Blood volume is reduced • Elevated cholesterol • Increased blood pressure • Cardiomegaly • Bradycardia
Alimentary System • Modest weight gain • Decreased appetite • Constipation
Nervous System • Essential for development of central nervous system in fetus and newborns • Slowing of intellectual functions • Psychiatric disorders • Myxedema coma • Hearing loss • “hung-up reflexes”
Muscular/Skeletal System • Muscle aches and stiffness • Increased muscle mass • Growth failure in children • Delayed maturation of bone
Fluids/Electrolytes • Decreased renal blood flow • Delay in water excretion • Hyponatremia
Hematopoietic System • Normocytic normochromic anemia • High incidence of pernicious anemia associated with hypothyroidism
Reproductive Function • Sexual immaturity • Delayed or precocious puberty • Galactorrhea • Diminished libido • menorrhagia
Laboratory • Free T4 • TSH • Thyroid antibodies • Thyroid peroxidase antibodies (microsomal antibodies) • Thyroglobulin antibodies
Radioactive T3 T4 TBG Resin
Euthyroid T4 TBG Resin
Hypothyroid T4 T3RU TSH TBG Resin
TBG Deficiency T4 T3RU TSH N TBG Resin
Treatment • Oral L-thyroxine therapy • 5-10 ug/kg in newborns • 1-2 ug/kg in adults