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 birth

Most 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 Caucasians

More 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 thyroid

Thyroid aplasia

Thyroid hypoplasia

Inborn errors of thyroxine synthesis

Defects in thyroid peroxidase activity

Abnormalities in iodine transport

Production of abnormal thyroglobulin

Iodotyrosine deiodinase deficiency

*Etiology (con’t)

Maternal antibody-mediated

Central

Won’t be detected on NBS using TSH screening

Iodine deficiency/ Iodide excess

Transient

Non-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 labs

Free T4

Total T4

T3

TSH

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

*Management

Goals are normal growth and good cognitive outcome

Levothyroxine

10-15 mcg/kg/day

50mcg/day recommended for all term and full-sized infants

10-15mcg/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 TSH

At 2 and 4 weeks after initiation of therapy

Q1-2 mos during 1st 6 postnatal mos

Q6mos from 6mos-3yrs

Q6-12 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 old

Caused by failure of the hypothalamic-pituitary-thyroid axis

Primary: thyroid

Secondary: pituitary

Tertiary: hypothalamus

Epidemiology

Most cases are sporadic

Only 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 diseases

Occurs more commonly in patients with Down syndrome or Turner syndrome

*Causes of Acquired Hypothyroidism

Primary

Hashimoto (AI) thyroiditis

Postablation

Irradiation to the neck

Medications

Iodine deficiency

Late onset congenital hypothyroidism

Secondary/ Tertiary

Craniopharyngioma

Neurosurgery

Cranial irradiation

Head Trauma

*Signs and Symptoms

Decline in linear growth

Fatigue

Constipation

Cold intolerance

Decline in school performance

Weight gain

Irregular menstrual periods

Dry skin

Hair loss

Growth failure

*Lab Evaluation

~Use of U/S and

thyroid scan in

diagnosis

usually not

warranted.

Management

Levothyroxine

Age 6-12 mos: 5-8 mcg/kg

Age 1-3 years: 4-6 mcg/kg

Age 3-10 years: 3-5 mcg/kg

Age 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 TSH

Normal free T4 by equilibrium dialysis

Corrects for low TBG

Low TBG

Thyroid hormone resistance

Normal labs with clinical features of hypothyroidism

Thanks for your attention!

Noon Conference: Neonatal Surgical Emergencies, Dr.

Mumphrey!!!