1. Clinical Application Hypothyroidism and Hyperthyroidism Gail Nunlee-Bland, M.D.

2. Hypothyroidism Clinical condition associated with decreased function of the thyroid gland and a decrease in the circulating level of thyroid hormones

7. Hypothyroidism Causes 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)

8. Primary Atrophic Hypothyroidism Autoimmune thyroiditis (Hashimoto’s disease) Postablative I 131 or surgery Athyreotic due to ageneisis or dysplasia Unresponsivenes to TSH

9. Goitrous Hypothryoidism Hashimoto’s thyroiditis Endemic iodine deficiency Iodine-induced Antithyroid agents

10. Central Hypothyroidism Secondary (pituitary) hypothyroidism Panhypopituitarism Isolated TSH deficiency Abnormal TSH synthesis or receptor defect Hypothalamic hypothyroidism

11. 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

12. 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

13. 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

14. Hashimoto’s Thyroiditis Most common cause of goitrous hypothyroidism in iodine sufficient areas Autoimmune

15. 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

16. Antithyroid Agents Lithium Para-aminosalicylic acid Phenylbutazone Topically applied resorcinol ethionamide Soybean in infant formulas

17. 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

18. 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

19. Clinical Features

25. Cardiovascular Cardiac output is decreased Peripheral vascular resistance is increased Blood volume is reduced Elevated cholesterol Increased blood pressure Cardiomegaly Bradycardia

27. Alimentary System Modest weight gain Decreased appetite Constipation

28. 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”

29. Muscular/Skeletal System Muscle aches and stiffness Increased muscle mass Growth failure in children Delayed maturation of bone

30. Fluids/Electrolytes Decreased renal blood flow Delay in water excretion Hyponatremia

31. Hematopoietic System Normocytic normochromic anemia High incidence of pernicious anemia associated with hypothyroidism

32. Reproductive Function Sexual immaturity Delayed or precocious puberty Galactorrhea Diminished libido menorrhagia

33. Laboratory Free T4 TSH Thyroid antibodies –Thyroid peroxidase antibodies (microsomal antibodies) –Thyroglobulin antibodies

34. TBG Resin Radioactive T3 T4

35. TBG Resin T4 Euthyroid

36. TBG Resin Hypothyroid T4  T3RU  TSH 

37. TBG Resin TBG Deficiency T4  T3RU  TSH N

38. Primary Hypothyroidism

39. TBG Deficiency

40. Treatment Oral L-thyroxine therapy –5-10 ug/kg in newborns –1-2 ug/kg in adults