Because the treatment is simple, effective, and inexpensive, most of the developed world utilizes newborn screening with blood thyroid stimulating hormone (TSH) levels to detect congenital hypothyroidism.

Infants born with congenital hypothyroidism may show no effects, or may display mild effects that often go unrecognized as a problem: excessive sleeping, reduced interest in nursing, poor muscle tone, low or hoarse cry, infrequent bowel movements, significant jaundice, and low body temperature.

However, recent studies have shown an increase in the number of cases caused by gland in situ (termed dyshormonogenesis when there is a defect in hormone production).

One Japanese study found a statistical correlation between certain organochlorine insecticides and dioxin-like chemicals in the milk of mothers who had given birth to infants with congenital hypothyroidism.

[3] Neonatal hypothyroidism has been reported in cases of infants exposed to lithium, a mood stabilizer used to treat bipolar disorder, in utero.

[citation needed] Congenital hypothyroidism can also occur due to genetic defects of thyroxine or triiodothyronine synthesis within a structurally normal gland.

[1] If the TSH is high, or the T4 low, the infant's doctor and parents are called and a referral to a pediatric endocrinologist is recommended to confirm the diagnosis and initiate treatment.

[citation needed] Most children born with congenital hypothyroidism and correctly treated with thyroxine grow and develop normally in all respects.

Even most of those with athyreosis and undetectable T4 levels at birth develop with normal intelligence, although as a population academic performance tends to be below that of siblings and mild learning problems occur in some.

[2][11][12][13][14] The differences in CH-incidence are more likely due to iodine deficiency thyroid disorders or to the type of screening method than to ethnic affiliation.