OBSERVATIONS ON MATURATION OF THYROID FUNCTION IN EARLY FETAL LIFE
OBSERVATIONS ON MATURATION OF THYROID FUNCTION IN EARLY FETAL LIFE
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DOI：
10.1172/jci106397
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发表时间：
1970-01-01
影响因子：
15.9
通讯作者：
BLIZZARD, RM
中科院分区：
文献类型：
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作者：
GREENBERG, AH;CZERNICHOW, P;BLIZZARD, RM
取21例经治疗流产后的正常胎儿的血清标本，用于精神医学指征。胎儿头臀长度为5.2~22.5 cm，对应的胎龄为65~168天。血甲状腺激素测定采用改良的Murphy-Patty方法，在妊娠78天时检测出第二个最小的胎儿。此后迅速增加，与冠臀长呈显著线性相关(r=0.800，P<；0.001)。游离甲状腺素(FT_4)与胎龄呈线性关系(r=0.908，P<；0.001)，但在18-20周时达到足月水平。于妊娠78天测定促甲状腺激素(TSH)放射免疫水平。随着妊娠的推进，水平迅速升高，因此到16周时，几乎所有的婴儿都在足月儿的范围内。妊娠16周后，血清TSH值通常大于4.0TSHU/cc，高于正常儿童。血清μ水平与总甲状腺激素无相关性。而TSH和FT4呈平行上升，且呈显著正相关。提示胎儿促甲状腺激素的分泌从妊娠早期就开始对FT4水平作出反应，可能早到11wk。在妊娠78天的胎儿中检测到甲状腺激素结合球蛋白(μg/100ml)。水平迅速升高，与血清甲状腺激素的升高平行，并与冠部长度保持线性相关(r=0.864，P<；0.001)。妊娠14~24周胎儿的甲状腺激素结合前白蛋白结合力(TBPA)与足月时相当。当检查甲状腺激素结合蛋白(T4-131I)示踪量在两种甲状腺激素结合蛋白之间的分布时，发现很大一部分在妊娠早期与TBPA和白蛋白结合。随着胎儿成熟度的增加，结合TBG的比例呈线性下降。在妊娠20周时，尽管脐血总胆红素含量仅为7.7μg/100ml，但仍能结合78%的示踪剂，这可能是由于妊娠期间血清总胆红素和白蛋白浓度相对较低所致。为胎儿和新生儿计算的理论结合常数与正常成年男性和女性的估计值相似。
Serum samples were obtained from 21 normal human fetuses after therapeutic abortion for psychiatric indications. Fetal crown-rump length ranged from 5.2 to 22.5 cm, corresponding to the gestational age of 65-168 days.Serum thyroxine, assayed by a modification of the Murphy-Pattee method, was identified in the second smallest fetus examined at 78 days gestation. Thereafter it increased rapidly, maintaining a significant linear correlation with crown-rump length until term (r= 0.800,P< 0.001). Free thyroxine (FT4) also increased in a linear relation to gestational age (r= 0.908,P< 0.001), but reached term levels by 18-20 wk. Radioimmunoassayable thyroid-stimulating hormone (TSH) was detected at 78 days gestation. Levels increased rapidly with advancing gestation, so that by 16 wk almost all were within the range of term infants. After 16 wk gestation, levels were usually greater than 4.0 μU/cc, higher than that seen in normal children.No correlation was demonstrated between the serum TSH levels and total thyroxine. TSH and FT4, however, increased in a parallel manner with a significant positive correlation. This suggested that fetal TSH secretion was responsive to FT4 levels from very early in gestation, possibly as early as 11 wk.Thyroxine-binding globulin (TBG) was detected in a fetus of 78 days gestation (1.4 μg/100 ml). Levels increased rapidly, paralleling the rise in serum thyroxine and maintaining a linear correlation with crownrump length (r= 0.864,P< 0.001). Thyroxine-binding prealbumin binding capacity (TBPA) in fetuses 14-24 wk gestation was comparable with that seen at term.When examining the distribution of tracer amounts of thyroxine-131I (T4-131I) between the thyroxine-binding proteins, it was found that a major fraction was bound to TBPA and albumin during the early part of gestation. This decreased linearly with maturation of the fetus as the fraction bound to TBG increased. By 20 wk gestation fetal TBG was able to bind 78% of tracer despite a TBG capacity of only 7.7 μg/100 ml. This appeared to be the result of relatively low concentrations of TBPA and albumin during this period of gestation. The theoretical association constant calculated for fetal and newborn TBG was found to be similar to that estimated for normal adult males and females.Images