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Griffin Bullock


  • Elevated TSH and low FT4 (primary hypothyroidism)
    • Hashimoto’s (autoimmune) thyroiditis, iodine deficiency, drugs (amiodarone, dopamine antagonists), adrenal insufficiency, thyroid hormone resistance (genetic), non-thyroidal illness (recovery phase), post-surgery or ablation for hyperthyroidism
  • Elevated TSH and normal FT4: subclinical hypothyroidism

  • Low-Normal TSH, low FT4: central hypothyroidism, sick euthyroid


  • Often non-specific and vague: fatigue, cold intolerance, weight gain, constipation, dry skin, myalgia, edema menstrual irregularities, depression, mental dysfunction

  • Goiter, bradycardia, diastolic hypertension, delayed relaxation following reflex testing

  • Lab abnormalities: microcytic anemia, hypercholesterolemia, hyponatremia, elevated CK


  • TSH: If elevated repeat TSH and obtain T4

  • Lipid panel, CBC, BMP


  • Treatment required if ↓ T4, significantly ↑ TSH (>10), or symptoms with any lab abnormality

  • Titrate therapy to a normal TSH (unless central hypothyroidism, then target free T4 levels)

  • Observation of asymptomatic pts with subclinical hypothyroidism (normal T4, mild ↑ TSH)

  • Treatment is with formulation of T4 (full replacement is approximately 1.6 mcg/kg/day)

  • Initial Dose:

    • Young/healthy patients: full anticipated dose

    • Older patients or patients with CAD: 25-50 mcg daily

  • Increased doses required for: pregnancy, estrogen therapy, weight gain, PPI therapy, GI disorders (↓ absorption), ferrous sulfate therapy

Additional information

  • Pts should take Levothyroxine alone, 1 hr prior to eating to ensure appropriate absorption

  • Of note, missed doses can be taken along with the next dose

  • Symptoms improve in 2-3 weeks. TSH steady state requires 6 weeks

  • Dose can be titrated every 6 weeks based on TSH

  • Pregnancy: Pregnancy causes lab changes due to differing levels thyroid binding globulin. Use tables based on trimester to interpret values

    • TPO antibody testing should be conducted if abnormal as this affects risk of complications
  • Hypothyroid pts are at increased risk for preeclampsia, placental abruption, preterm labor/delivery

  • Refer to endocrine for close monitoring and adjustment to avoid fetal complications

  • Inpatients who are pregnant and have abnormal TFTs warrant endocine consult.

Last update: 2022-06-20 02:21:13