Hypothyroidism in Kiddos

Clinical manifestations:

  • 80% (!!) are asymptomatic
  • Goiter
  • Poor growth velocity and short stature
    • Bone age and height < chronological age
  • Abnormal pubertal development
    • Usually delayed, but sometimes precocious puberty occurs
  • Decline in school performance
    • Most of the time, children have a decline in school performance and cognitive functioning, but occasionally if children are less active from hypothyroidism, their school performance actually improves, which is one of the factors that can lead to a delay in diagnosis
  • Sluggishness/lethargy
  • Cold intolerance
  • Constipation
  • Dry skin/brittle hair and nails
  • Pale, cool skin
  • Facial puffiness
  • Weight gain
  • Non-pitting edema (myxedema)
  • Pseudohypertrophy of muscles 
  • Bradycardia 
  • Pleural or pericardial effusions

Lab findings

  • Normocytic or macrocytic hypoproliferative anemia
  • Hyperlipidemia (most commonly hypertriglyceridemia and low HDL)
  • Hyponatremia (reduced free water clearance)
  • Elevated CK
  • Reversible elevation in creatinine

Levothyroxine dosing

  • 1-5yo: 4-6 mcg/kg daily
  • 6-10yo: 3-4 mcg/kg daily
  • 11-18yo: 2-3 mcg/kg daily
  • adults: 1.6 mcg/kg IBW daily

Note: avoid taking levothyroxine with soy, fiber, iron, or calcium

Target Goal: 

  • TSH 1-3 (keep on the low side if goiter)
  • FT4 reference range
  • Repeat TFTs in 6-8 weeks

Fun fact: If someone is subclinical hypothyroidism (elevated TSH but normal T4), expert opinion suggests starting treatment either when TSH >10, if there is a goiter, or if there are clinical symptoms of hypothyroidism


Monitoring

  • Recheck TFTs every 6-12 months if dose is stable
  • Adjust by 12.5 to 25mcg at a time
  • After any change in dose, recheck TFTs in 6-8 weeks
  • Levothyroxine has a long half life – can increase the dose by doubling the dose on 1-2 days each week before a new set of pills arrive! (Same idea for decreasing the dose – just have the patient skip 1 day each week)

Blog post based on Med-Peds Forum case presentation by Lindsey Mahoney, PGY3, and Sam Masur, PGY3

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