Newborn screening programs for the detection of congenital hypothyroidism have dramatically shortened the time before treatment is begun. However, concern still exists about central nervous system sequelae which may persist due to a period of untreated intrauterine hypothyroidism. Presence of polyhydramnios led to the ultrasound diagnosis of a fetal goiter. Hypothyroidism was confirmed at 34 weeks gestation by percutaneous fetal blood sampling, which revealed an elevated TSH (186 mU/L) and a low T4 (19.3 nmol/L). Intraamniotic fluid injections of 500 micrograms levothyroxine sodium (T4) every 10-14 days increased fetal serum T4 (59.2 nmol/L), decreased fetal serum TSH (14 mU/L), decreased amniotic fluid TSH, and decreased the size of the fetal goiter. The infant was born at term without perinatal complications. Thyroid function studies on cord blood were normal (T4, 109.4 nmol/L; TSH, 1.3 mU/L), and the infant was discharged on oral T4. Follow-up examination at age 6 weeks revealed that the infant was developmentally normal and clinically and chemically euthyroid. Intrauterine T4 therapy can suppress fetal TSH and treat fetal hypothyroidism despite hypothyroid levels of serum T3. Highly sensitive TSH assays may allow the use of amniotic fluid TSH as a marker for fetal hypothyroidism.
Summaryplasma CAT. In an earlier studv of ~l a s m a CAT in the fetal sheepThe present studies were designed to assess the individual effects of delivery and umbilical cord cutting on the stimulation of the sympatho-adrenal system during parturition. Pregnant ewes with time-dated singleton pregnancies were used in an acutely exteriorized fetal lamb model with an intact umbilical circulation. We observed a minimal, transient elevation in plasma catecholamines (CAT) coincident with the operative procedures and delivery. Subsequent cord clamping was observed to evoke a rapid and marked increase of both norepinephrine and epinephrine (E), maximal at 5 min and persisting over the 4 h r study period. Animals could be grouped on the basis of the observed CAT responses, severity of postpartum acidosis, the extent of free fatty acid (FFA) mobilization and degree of postpartum hypothermia. A blunted FFA response and slower correction of hypothermia were observed in the more acidotic animals despite higher CAT concentrations. One group of four animals had high peak CAT concentrations, 32,000 p g / d norepinephrine and 35,000 p g / d E, a deep nadir in pH of 6.88 k 0.09, a 2-hr delay in maximal FFA mobilization and slower correction of hypothermia. The other group of four animals had peak norepinephrine of 2800 pg/ml and E of 1100 pg/d, a nadir in pH of 7.09 * 0.08, maximal plasma FFA concentration by 1 hr after cord cutting and a higher nadir in body temperature 35.7 versus 32.S°C. The results demonstrate that umbilical cord cutting itself is a potent stimulus for fetal CAT release and FFA mobilization. Acidosis is capable of markedly augmenting E release in the mature fetus and obtunding chemical thermogenesis. SpeculationThe marked catecholamine surge evoked by umbilical cord cutting at the time of birth appears to be a major factor triggering the metabolic events facilitating ada~tation to extrauterine life. The mechanism for the catechoiamine release is uncertain. However, cardiovascular and chemoreceptor mediated activation of autonomic nervous system activity probably are involved. The separate contributions of increased p&tganglionic neurosympathetic activity and adrenal-medullary catecholamine release to n w natal adaptation should be explored further.Previous work in a variety of animals (9) and man (15) suggests that the sympatho-adrenal system is relatively mature at term. Substantial catecholamine release has been observed in the near term fetal sheep in response to a variety of stimuli including hypoxia (8), maternal blood volume depletion (2), and maternal exercise (18). In the human newborn we and others (13,21,23) have shown striking elevations of plasma catecholamine (CAT) in both umbilical blood samples and neonatal blood drawn in the first minutes and hours of life. In each of the studies reported to date there was a marked umbilical artery to umbilical vein CAT concentration difference suggesting a fetal origin for the cord before and during parturition h e demonstrated basal circulating levels at great...
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