Acute release of thyrotropin in the newborn

Abstract

A B S T R A C T Measurements of serum thyrotropin(TSH) concentrations were conducted in maternal and fetal blood during labor and delivery and the early postnatal and neonatal periods. Mean TSH concentration was significantly higher in cord blood (9.5 AU/ml) than maternal blood (3.9 /U/ml), a finding suggesting a fetalmaternal TSH gradient at term. Serum TSH concentration in the newborn increased rapidly to mean levels of 60 AU/ml at 10 min and 86 AU/ml at 30 min of age.Between 30 min and 3-4 hr serum levels decreased rapidly, then fell more gradually to a mean concentration of 13 AU/ml at 48 hr. The half-time of the decrease in serum TSH concentration between 30 and 90 min was 77 min, a value slightly greater than the half-time of disappearance of radioiodinated TSH measured in adults. This indicates that the early high rate of TSH secretion in the newborn ceases by 30 min, and that the rapid rise and fall in serum TSH concentrations may represent release of stored pituitary TSH. A more chronic TSH hypersecretion persisted throughout the first 24-48 hr of extrauterine life. Measurements of serum PBI concentrations were conducted in a separate group of maternal and cord blood samples and in the newborn infants during the first 48 hr of extrauterine life to relate the TSH and serum hormonal iodine concentration changes. Serum protein-bound iodine (PBI) concentrations were similar in maternal and cord blood, increased significantly by 4 hr of age in the newborn, and peaked at about 24 hr, presumably in response to the TSH hypersecretion. The pattern of TSH hypersecretion was similar in infants delivered vaginally and by caesarean section. Maternal serum TSH concentrations were stable throughout the perinatal period. Warming the infants at 99-103'F during the first 3 hr of life did not prevent the early, acute release of thyrotropin. Cooling of warm infants at room temperature (72-780F) between 3 and 4 hr resulted in a decrease in mean rectal temperature of 3.3XF and produced a significant increment in serum TSH concentration. These data suggest

Serum Triiodothyronine, Total Thyroxine, and Thyroxine to Triiodothyronine Ratios in Paired Maternal-Cord Sera and at One Week and One Month of Age

“…The stimulus for the increased secretion of TSH has not been elucidated. Exposure to cold has been postulated; however, Fisher and Odell [8] demonstrated levels of TSH of the same magnitude as those found in cord blood to be present in blood obtained from scalp veins before delivery. The low circulating 710 MONTALVO ET AL.…”

“…The low levels of T 3 in the presence of normal T 4 levels in cord blood tend to indicate that in the fetus either T 3 secretion by the fetal gland is decreased or that peripheral conversion of T 4 /T 3 is markedly decreased. Pituitary thyrotropic hormone has been shown to be elevated in cord blood and to remain elevated for at least 72 hr after birth [3,8,21,23]. The stimulus for the increased secretion of TSH has not been elucidated.…”

Thyroid function profile in cord blood and postnatal changes at 24 and 72hours in healthy term Nigerian neonates

“…The temperature fluctuates within wide limits from about 15 0 C during the cold night to over 40 0 C during the hot days 17 . The low ambient temperature during the cold season could predispose to higher TSH surge 18 . Most of the ethnic groups are represented, but the majorities are the indigenous Hausas/Fulani population.…”

Amniotic fluid thyrotropin (TSH) following maternal administration of thyrotropin releasing hormone

“…In the newborn, the half life of endogenous TSH is 77 minutes [8]. It is not known how fetal TSH reaches the amniotic fluid.…”