Signs of hypothyroidism usually are difficult to
diagnose at or immediately after birth. In severe cases, it may take a few
weeks until symptoms become apparent. In milder cases, diagnosis may be
delayed for months or even longer. Screening programs with measurement of
TSH and T4 are important because congenital hypothyroidism is one of
the most common preventable causes of mental retardation. Early signs may
include an abnormally high birth weight, delayed passage of meconium,
constipation, and a large abdomen. Later symptoms include persistent neonatal
icterus, feeding difficulties with little appetite, failure to thrive, choking spells, respiratory distress and apneas
(partly as a result of macroglossia and nasal obstruction), wide anterior and posterior fontanelles
(an important and common sign), hoarse voice, umbilical hernia, and
disturbances in thermoregulation with temperatures often below 35°C,
leading to cold and mottled skin. Somnolence and lethargy, bradycardia
(despite frequently present anemia) and cardiomegaly, pericardial and
pleural effusions, and genital and peripheral edemas are frequent findings.
Physical and psychomotor development are delayed and become more obvious at
3 to 6 months of age in severe cases. The changes are more subtle in milder
cases and therefore are more difficult to detect. Dysmorphic features may
include coarse, brittle hair with low anterior hairline, hypertelorism,
depressed nasal bridge, constantly open mouth with protruding tongue
secondary to macroglossia, short and thick neck, short stature, wide hands
with brachydactyly, and generalized muscular hypotonia with a clumsy gait. The
skin often appears dry and scaly. In endemic cretinism, the above described
findings are often accompanied by deaf-mutism and motor dysfunction with
spasticity.