Thyroid

Subclinical Hypothyroidism

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Subclinical Hypothyroidism, Sick Euthyroid Syndrome, Euthyroid Sick Syndrome

  • See Also
  • Definition
  1. Elevated TSH with normal Free T4
  • Epidemiology
  1. Incidence Older Men: 2-8%
  2. Incidence Older Women: 5-10%
  • Precautions
  1. Normal TSH range increases with age up to 7.5 mIU/L for an 80 year old patient (see TSH)
  • Indications
  • Treatment
  1. Thyroid Stimulating Hormone (TSH) > 10 mU/ml or
  2. Thyroid peroxidase Antibody positive or
  3. Symptoms with persistent mildly elevatad TSH
    1. Depression
    2. Fatigue, Consgtipation, Cold intolerance, Hair Loss
    3. Hyperlipidemia
    4. Goiter
    5. Hyperhomocysteinemia
    6. Coronary Artery Disease or Cardiac Risk Factors
    7. Pregnancy or expected pregnancy
  • Complications
  1. Coronary Artery Disease (increased risk in elderly)
    1. Treating patients with Subclinical Hypothyroidism may lower cardiovascular disease risk
    2. Biondi (2002) Ann Intern Med [PubMed]
  • Management
  1. See Hypothyroidism
  2. Levothyroxine
    1. See Levothyroxine for standard dosing protocol if TSH >10 mIU/L
    2. Dosing (indicated for TSH <10 mIU/L and indications listed above)
      1. Younger than age 50 years
        1. Start at 50 mcg daily and increase by 25 mcg every 6 weeks until goals met
      2. Over age 50 years
        1. Start at 12.5 to 25 mcg daily and increase by 12.5 to 25 mcg every 6 weeks until goals met
    3. Goals for treating Subclinical Hypothyroidism
      1. LDL Cholesterol falls
      2. Hypothyroidism symptoms improve
      3. TSH normalizes <4.0
  3. Precautions: Avoid overtreatment with excessive Levothyroxine
    1. Risk of Osteoporosis worsening, Atrial Fibrillation
    2. Stop Levothyroxine if persistently subclinical (TSH <10) and no symptom improvement at 3-6 months
  • Monitoring
  1. Aim to lower Serum TSH to mid-normal: 1 to 3 mU/ml
  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
  • References
  1. (2017) Presc Lett 25(1):4
  2. (2012) Presc Lett 19(6): 34
  3. Svec (2001) CMEA Medicine Lecture, San Diego
  4. Hueston (2001) Am Fam Physician 64(10):1717-24 [PubMed]
  5. Adlin (1998) Am Fam Physician 57(4):776-80 [PubMed]
  6. Vanderpump (1995) Clin Endocrinol 43:55 [PubMed]