Changes in thyroid function in a newborn:

– In the first 30 minutes after birth, the concentration of TSH in the serum of the newborn rapidly increases to 80 mU / L (probably due to physiological stress accompanying the birth and bandaging of the umbilical cord). During the first week of life, the concentration of TSH gradually decreases to 10 mU / L.  

– A rapid increase in the level of TSH causes an equally rapid increase in the concentrations of total T4 and total T3 ; they reach the values ​​characteristic of thyrotoxicosis in adults. Over the next weeks, the levels of total T4 and total T3 gradually decrease .      

Neurological consequences of congenital hypothyroidism :  

– Pathogenesis. In experiments on animal embryos, it was shown that thyroid hormone receptors are present both in neurons and in glial cells of the brain . Thyroid hormones stimulate the proliferation and migration of neuroblasts , the growth of axons and dendrites , the differentiation and myelination of oligodendrocytes . Hypothyroidism inhibits the expression of a gene encoding a myelin protein .                  

– Delayed mental development . The earlier hypothyroidism is detected and treatment is started, the better the prognosis of mental development. Even if treatment of the child begins in the first 3 months of life, mental development is delayed: in children with hypothyroidism older than 2 years, IQ = 89, i.e., slightly lower than normal. It is estimated that the prevalence of hypothyroidism among the mentally retarded in special boarding schools reaches 5%.  

– Other neurological disorders. In addition to decreased cognitive functions , ataxia , impaired coordination of movements , awkwardness of gait , muscle hypotension , muscle spasticity , speech , hearing impairment ( sensorineural hearing loss ) and vision ( strabismus ) can be observed .                  

For the prevention of mental retardation and neurological disorders in children with congenital hypothyroidism, mass screening programs for newborns have been developed and are currently underway. The main goal of such programs is the early (in the first weeks of life) diagnosis and therapy of congenital hypothyroidism.