Endocrinology Book

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Subclinical HypothyroidismAka: Sick Euthyroid Syndrome

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  1. See Also
    1. Hypothyroidism
  2. Definition
    1. Elevated TSH with normal Free T4
  3. Epidemiology
    1. Incidence Older Men: 2-8%
    2. Incidence Older Women: 5-10%
  4. Indications for treatment
    1. Thyroid Stimulating Hormone (TSH) > 10 mU/ml
    2. Clinical Features present
      1. Depression
      2. Fatigue
      3. Hyperlipidemia
      4. Goiter
      5. Hyperhomocysteinemia
      6. Coronary Artery Disease or Cardiac Risk Factors
      7. Pregnancy or expected pregnancy
  5. Contraindications for treatment
    1. Osteoporosis or Fracture risk
  6. Complications
    1. Coronary Artery Disease (increased risk in elderly)
      1. Biondi (2002) :
  7. Management
    1. See Hypothyroidism
    2. Levothyroxine
      1. Dosing
        1. Young: start at 50 ug qd
        2. Elderly: start at 12.5 to 25 ug qd
      2. Goals for treating subclinical Hypothyroidism
        1. LDL Cholesterol falls
        2. Hypothyroidism symptoms improve
        3. TSH normalizes <4.0
  8. Monitoring
    1. Aim to lower Serum TSH to mid-normal: 1-3
  9. Course: Risk of longterm progression to overt Hypothyroidism
    1. TSH 4-6 mU/ml: No increased risk of future Hypothyroidism
    2. TSH >6 mU/ml: 27-42% risk of future Hypothyroidism
    3. TSH >6 mU/ml and Thyroid Peroxidase Antibody positive: >55% risk of future Hypothyroidism
  10. References
    1. Svec (2001) CMEA Medicine Lecture, San Diego
    2. Hueston (2001) Am Fam Physician 64(10):1717
    3. Adlin (1998) Am Fam Physician 57(4):776
    4. Vanderpump (1995) Clin Endocrinol 43:55

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