Cretinism
Definition
Congenitial hypothyroidism - in the newborn
Aetiology
This can occur because of
- An anatomic defect in the gland
- An inborn error of thyroid metabolism
- Iodine deficiency.
The morbidity can be reduced to a minimum by early diagnosis and treatment
Causes
Endemic cretinism - iodine deficiency
Exacerbated by naturally occurring goitrogen
Dysgenesis
Agenesis
Ectopy (lingual or sublingual thyroid gland)
Inborn errors of thyroid hormone metabolism
TSH unresponsiveness (ie, TSH receptor abnormalities)
Impaired ability to uptake iodide
Peroxidase, or organification, defect (ie, inability to convert iodide to iodine)
Pendred syndrome, a familial organification defect associated with congenital deafness
Thyroglobulin defect (ie, inability to form or degrade thyroglobulin)
Deiodinase defect
Thyroid hormone resistance (ie, thyroid hormone receptor abnormalities)
Maternal autoimmune disease (transient or permanent)
Iatrogenic causes - Maternal use of thioamides, iodine excess, radioactive iodine therapy
TSH or thyrotropin-releasing hormone (TRH) deficiencies
Clinical Features
Symptoms and signs include the following:
Decreased activity
Large anterior fontanelle
Poor feeding and weight gain
Small stature or poor growth
Jaundice
Constipation
Hypotonia
Hoarse cry
Often, they are described as "good babies" because they rarely cry and sleep most of the time.
Family history of similar infants or family members with unexplained mental retardation.
Maternal history of a thyroid disorder and mode of treatment, whether before or during pregnancy
Birthweights less than 2,000 g or more than 4,500 g.
Coarse facial features
Macroglossia
Large fontanelles
Umbilical hernia
Mottled, cool, and dry skin
Developmental delay
Pallor
Myxedema
Goiter
Other birth defects, mainly atrial and ventricular septal defects.
Differential Diagnosis
Hypopituitarism
Hypothyroidism
Panhypopituitarism
Thyroiditis
Lab Studies
radioimmunoassay for thyroid-stimulating hormone (TSH) and thyroxine (T4) from blood spots on filter paper, obtained for neonatal screening tests.
(T3, T4, TSH estimation)
Maternal or neonatal antithyroid antibodies estimation
TBG levels estimation
With TBG deficiency shows a low total T4 level and a TSH level within the reference range. Free T4 and T3 levels are within the reference range.
Imaging Studies
Thyroid scanning (using technetium-99m or iodine-123)
Ultrasonography
X-Ray Knee AP and Lateral views - absent distal femoral - poor prognostic sign (the epiphysis appears at 36 weeks)
Treatment
LevothyroxinePill - crushed in a spoon; dissolved with a small amount of breast milk, water or other liquid immediately before administration. The pills should not be mixed in a full bottle.
Monitor infants for indications of overtreatment (eg, nervousness, hyperactivity, anxiety, tachycardia, palpitations, tremors, fever, diaphoresis, abdominal symptoms, weight loss);
Follow up
Children with congenital hypothyroidism should be monitored clinically and biochemically. Clinical parameters should include linear growth, weight gain, developmental progression, and overall well-being.
Laboratory measurements of T4 (total or free T4) and TSH should be repeated 4-6 weeks after initiation of therapy, then every 1-3 months during the first year of life and every 2-4 months during the second and third years. In children aged 3 years and older, the time interval between measurements may be increased, depending on the reliability of the patient's caretakers. As dosage changes are made, testing should be more frequent.
Formal developmental and psychoneurological evaluations should be considered in all infants with congenital hypothyroidism. Such evaluations are especially important in children whose treatment was delayed or inadequate.
