Hypothyroidism!

2014 Pediatrics in Review article
Epidemiology: ~1:2000-4000
- Common cause of treatable intellectual disability
Presentation: Few or no symptoms (~95%; hence need for newborn screen)
- Poor feeding, excessive sleepiness, not meeting milestones, edematous, poor tone, enlarged tongue, dry skin, jaundice, anemia
Causes: thyroid dysgenesis, iodine deficiency (most common cause in developing nations), maternal antibodies (anti-TSHr), medications, TSH receptor dysfunction, and hypothalamic/pituitary dysfunction
Diagnosis: Newborn screen (NBS) or targeted testing if symptoms present
Treatment: When NBS is abnormal treat immediately after sending confirmatory testing
- Replace T4 (levothyroxine) orally and refer to endocrinology
Prognosis: 30% of cases resolve as child grows. Early treatment and identification improves neurocognitive outcomes!

Epidemiology: ~1:1500
Presentation: declining height velocity, delayed puberty, change in school performance, cold intolerance, depression, carpal tunnel, constipation, weight gain (though less common than adults), edema, HLD, anemia, and hyponatremia
- HLD – caused by decreased lipid clearance
- Hyponatremia – may result from abnormal free water clearance
Associations: with other diseases: Trisomy 21, Turner syndrome, T1DM, and celiac disease

2012 AACE/ATA Clinical Practice Guidelines
Epidemiology: 1:300
- Female predominance
- Increases in prevalence with age
Presentation: Everything mentioned previously plus fertility issues and weight changes
Causes: primary hypothyroidism (autoimmune, radiation, thyroidectomy), medications (lithium, amiodarone, iodinated contrast, and iodine itself), or hypothalamic pituitary axis issues
Diagnosis
- Check TSH and free T4
- No need to check anti-TPO or anti-thyroglobulin
- Do not screen asymptomatic patients
- Do not routinely check T3
Treatment:
- T4 (levothyroxine) on an empty stomach
- Dosing is weight-based, age-specific and depends on pt comorbidities
- Recheck TSH six weeks after treatment initiated; adjust dose as needed once TSH normalizes and symptoms resolve; once maintenance dose is established can check labs yearly

2019 JAMA review
Defined as elevated TSH (5-10 uM/L range) in the presence of normal T4
May be useful to check for TPO antibodies given the 5% risk per year of converting to overt hypothyroidism if antibodies are present (Grade B)
Should be treated if pt becomes pregnant
Treat with levothyroxine if TSH >10 because of increased risk for CVD (Grade 2C)

ACOG and ATA recommend not routinely screening for hypothyroidism (Grade B)
Women considering pregnancy should have there levothyroxine dose optimized prior to becoming pregnant
Most women should anticipate having their dose of levothyroxine increased during pregnancy and frequent blood work

Congenital hypothyroidism is rare and will resolve ~30% of the time; prompt treatment should be initiated if NBS is abnormal even with confirmatory testing pending
Check TSH and T4 if exhibiting symptoms (don’t forget HLD). Remember the M&Ms!!!
Do not screen asymptomatic individuals
Do not routinely check T3
Rare in child and adolescents but commonly associated with other disease states diagnosed in this age group like Type 1 DM and Celiac disease
Not very useful to order TPO antibodies unless pt has subclinical hypothyroidism (increases risk of conversion to over hypothyroidism)
Levothyroxine dose is weight-based and varies by age and comorbidities (lower doses in elderly and individuals with CAD; higher dose in pregnancy)

*Blog post based on Med-Peds Forum talk by Roger Auth, PGY4

Brown Med-Peds Residency