Hypothyroidism!

QUICK HITS!

  • Remember your thyroid “M&Ms”! 
    • Movement
    • Metabolism
    • Mentation
  • Thyroid hormones–normal levels vary by age!

 


CONGENITAL 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!

HYPOTHYROIDISM IN CHILDREN & ADOLESCENTS!

  • 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  

HYPOTHYROIDISM IN ADULTS!

  • 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

SUBCLINICAL HYPOTHYROIDISM

  • 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) 

PREGNANCY

  • 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 

WHEN TO REFER?

  • Infants and children 
  • Poor response to therapy 
  • Thyroid nodule or goiter present 
  • Planning conception or pregnancy
  • Concern for central hypothyroidism 
  • Have other endocrine disorders like adrenal insufficiency or hypopituitarism 

SUMMARY

  • 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