HYPOTHYROIDISM:

HYPOTHYROIDISM:

Hypothyroidism result from deficient production of thyroid hormone or a defect in thyroid hormone receptors activity and the disorder may be manifested from birth or acquired during childhood.
ETIOLOGY:
Thyroid dysgenesis ( aplasia, hypoplasia ,or ectopic gland ) is the most common cause of congenital hypothyroidism accounting for 80% of cases ,10% are caused by an inborn error of thyroxin synthesis and 5% are the result of transplacental maternal thyrotropin –receptor blocking antibody .
The most common cause of acquired hypothyroidism is chronic lymphocytic thyroditis (autoimmune thyroid disease ) and its risk increase child with Dowen ,Turner and Klinefelter syndromes ,celiac disease ,diabetes M. ,Sjogren syndrome ,multiple sclerosis ,pernicious anemia ,Addison disease and ovarian failure .Other causes include complication of thyroid surgery ,heamosedrosis ,nephropathic cystenosis ,irradiation ,medications containing iodide and children with large heamangioma of the liver .
CLINICAL MANIFESTATIONS:
Most infants with congenital hypothyroidism are asymptomatic at birth because of transplacental passage of moderate amount of maternal T4 which provide fetal levels of 33% of normal at birth. Female to male ratio is 2/1 .
The clinician is dependent on neonatal screening test for diagnosis of congenital hypothyroidism .
Birth weight and length are normal ,but head size may be slightly increase because of myxedema of the brain .Prolongation of physiological jaundice ,caused by delayed maturation of glucronide conjugation may be the earliest sign .
Feeding difficulties , sluggishness ,lack of interest, somnolence and chocking spells during nursing are often present during the first month of life.
Respiratory difficulties due to large tongue ,apneic episodes ,noisy respirations ,nasal obstruction and typical respiratory distress syndrome . Affected infant cry little , sleep much ,have poor appetites and sluggish. Constipation that does not respond to treatment. The abdomen is large and umbilical hernia is usually present.
The temperature is subnormal often <35 and the skin cold and mottled .Edema of the genital and extremities may be present.
The pulse is slow and heart murmurs ,cardiomegaly and asymptomatic pericardial effusion are common