Good Morning!!

Morning Report

Tuesday, September 13th

Common Causative Agents:

•Procainamide•Hydralazine•Penicilliamine•(But you can also see drug-induced SLE with phenytoin, methimazole and many other medications)

Hypothyroidism

Congenital Hypothyroidism

Why worry?T4 is critical to the myelinization of the CNS during the first 3 years after birthMost preventable cause of potential intellectual disability (so you don’t want to miss it!!!)

Definition

In healthy newborns:Abrupt rise in TSH within 30-60 mins of delivery stimulates T4 secretion

TSH levels peak early, while T4 levels peak 24-36h after delivery

In premature newborns:Smaller increases in TSH lower T4 values

Immaturity of the hypothalamic-pituitary axis

Concurrent non-thyroid illnesses

Epidemiology

85% cases sporadic, 15% hereditary (AR)Incidence 1:4000 infants

More common in Hispanics and CaucasiansMore common in females (2:1)More common in twins

Longer the diagnosis and treatment are delayed, the lower the IQ

*Etiology

Thyroid dysgenesis (most common)Ectopic thyroidThyroid aplasiaThyroid hypoplasia

Inborn errors of thyroxine synthesisDefects in thyroid peroxidase activityAbnormalities in iodine transportProduction of abnormal thyroglobulinIodotyrosine deiodinase deficiency

*Etiology (con’t)

Maternal antibody-mediated Central

Won’t be detected on NBS using TSH screening

Iodine deficiency/ Iodide excessTransientNon-thyroid illness (euthyroid-sick syndrome)

*Symptoms and Signs•Birthweight and

length normal (? Increased HC)

•Open posterior fontanelle

•Umbilical hernia

•Lethargy/hypotonia

•Hoarse cry

•Feeding problems

•Constipation

•Macroglossia

•Dry skin

Laboratory TestingNewborn Screen

Most states use initial T4 testing with f/u TSH

Initial labsFree T4Total T4T3TSH

In all forms of congenital hypothyroidism, serum T4 is low and TSH is elevated, except for central hypothyroidism where both T4 and TSH are low

*ManagementGoals are normal growth and good cognitive outcomeLevothyroxine

10-15 mcg/kg/day50mcg/day recommended for all term and full-sized infants10-15mcg/kg for preterm infant using the higher range for infants with lower T4

Tablets only Do not mix with soy formula or any preparation with iron or calcium

*Management (con’t)

Quicker correction is better!Goal to keep serum TT4 or fT4 in upper half of normal range for age and have normal TSH

Serum T4 (or free T4) and TSHAt 2 and 4 weeks after initiation of therapyQ1-2 mos during 1st 6 postnatal mosQ6mos from 6mos-3yrsQ6-12 mos until growth is complete

*Prognosis

Babies born with congenital hypothyroidism who are appropriately treated within the first 2-6 postnatal weeks grow and develop NORMALLY!Children who are treated inadequately in the first 2-3 years after birth have IQs below those of unaffected children

6-15 point lower IQ in the severely affected Even if IQ was not affected, difficulties with gross/fine motor coordination, ataxia, altered muscle tone, strabismus, decreased attention span and speech

Acquired Hypothyroidism

Onset after 6 mo oldCaused by failure of the hypothalamic-pituitary-thyroid axis

Primary: thyroidSecondary: pituitaryTertiary: hypothalamus

Epidemiology

Most cases are sporadicOnly 10-15% are inherited

More common in females (2:1)Hashimoto thyroiditis most common cause

May occur by itself or in association with other AI diseasesOccurs more commonly in patients with Down syndrome or Turner syndrome

*Causes of Acquired Hypothyroidism

Primary Hashimoto (AI) thyroiditis PostablationIrradiation to the neckMedicationsIodine deficiencyLate onset congenital hypothyroidism

Secondary/ Tertiary

CraniopharyngiomaNeurosurgeryCranial irradiationHead Trauma

*Signs and SymptomsDecline in linear growthFatigueConstipationCold intoleranceDecline in school performanceWeight gainIrregular menstrual periodsDry skinHair loss

Growth failure

*Lab Evaluation

~Use of U/S and thyroid scan in diagnosis usually not warranted.

Management

LevothyroxineAge 6-12 mos: 5-8 mcg/kgAge 1-3 years: 4-6 mcg/kgAge 3-10 years: 3-5 mcg/kgAge 10-18 years: 2-4 mcg/kg

Serum free T4 and TSH levels q3-6 mos

Goal: fT4 in mid-normal range with TSH nml

Prognosis

Growth may not recover if:Hypothyroidism longstanding Diagnosed during puberty

Cognitive/ neurologic deficits unlikely if onset is after 2-3 yo

Other entities…Thyroid-binding globulin deficiency

Low TT4, low or normal serum fT4, normal TSHNormal free T4 by equilibrium dialysis

Corrects for low TBGLow TBG

Thyroid hormone resistanceNormal labs with clinical features of hypothyroidism

Thanks for your attention!

Noon Conference: Neonatal Surgical Emergencies, Dr. Mumphrey!!!