Timing and magnitude of increases in levothyroxine requirements during pregnancy in women with hypothyroidism
Timing and magnitude of increases in levothyroxine requirements during pregnancy in women with hypothyroidism
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DOI：
10.1056/nejmoa040079
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发表时间：
2004-07-15
影响因子：
158.5
通讯作者：
Larsen, PR
中科院分区：
文献类型：
--
作者：
Alexander, EK;Marqusee, E;Larsen, PR
背景：怀孕期间的甲状腺功能减退症与认知发育受损和胎儿死亡率增加有关。怀孕期间，母体甲状腺激素的需求量增加。尽管众所周知，患有甲状腺功能减退症的女性应该在怀孕期间增加左旋甲状腺素的剂量，但许多人都会出现生化甲状腺功能减退症。在这项前瞻性研究中，我们试图准确确定怀孕期间所需左旋甲状腺素调整的时间和量。方法：对计划怀孕的甲状腺功能减退症妇女在怀孕前和整个怀孕期间进行前瞻性观察。在受孕前、妊娠前三个月大约每两周测量一次甲状腺功能、人绒毛膜促性腺激素和雌二醇，此后每月测量一次。增加左旋甲状腺素的剂量，以在整个怀孕期间将促甲状腺素浓度维持在孕前值。结果：19 名妇女共怀孕 20 次，产下 17 名足月婴儿。在 17 次怀孕期间，需要增加左旋甲状腺素剂量。妊娠前半期，左旋甲状腺素的平均需求量增加了 47%（中位增加起始时间为妊娠 8 周），并在第 16 周达到稳定水平。这种增加的剂量一直持续到分娩。结论：左旋甲状腺素的需求量最早在妊娠第 5 周就会增加。鉴于母体甲状腺功能正常对于胎儿正常认知发育的重要性，我们建议患有甲状腺功能减退症的女性在确认怀孕后立即将左旋甲状腺素剂量增加约 30%。此后，应监测血清促甲状腺素水平并相应调整左旋甲状腺素剂量。
BACKGROUND:Hypothyroidism during pregnancy has been associated with impaired cognitive development and increased fetal mortality. During pregnancy, maternal thyroid hormone requirements increase. Although it is known that women with hypothyroidism should increase their levothyroxine dose during pregnancy, biochemical hypothyroidism occurs in many. In this prospective study we attempted to identify precisely the timing and amount of levothyroxine adjustment required during pregnancy.METHODS:Women with hypothyroidism who were planning pregnancy were observed prospectively before and throughout their pregnancies. Thyroid function, human chorionic gonadotropin, and estradiol were measured before conception, approximately every two weeks during the first trimester, and monthly thereafter. The dose of levothyroxine was increased to maintain the thyrotropin concentration at preconception values throughout pregnancy.RESULTS:Twenty pregnancies occurred in 19 women and resulted in 17 full-term births. An increase in the levothyroxine dose was necessary during 17 pregnancies. The mean levothyroxine requirement increased 47 percent during the first half of pregnancy (median onset of increase, eight weeks of gestation) and plateaued by week 16. This increased dose was required until delivery.CONCLUSIONS:Levothyroxine requirements increase as early as the fifth week of gestation. Given the importance of maternal euthyroidism for normal fetal cognitive development, we propose that women with hypothyroidism increase their levothyroxine dose by approximately 30 percent as soon as pregnancy is confirmed. Thereafter, serum thyrotropin levels should be monitored and the levothyroxine dose adjusted accordingly.