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Re: Fw: Reenviar: Fw: Asking about therapeutic with l propylthiouracil.
From: Carlos Brito (clbmtoc@telcel.net.ve)
Sun Aug 3 08:26:54 2003
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Casualmente le oyeron y le sugieren ...July 2003 • Volume 189 • Number 1 Editorial Umbilical blood sampling in women with thyroid disease in pregnancy: Is it necessary? Sarah Kilpatrick, MD, PhD [MEDLINE LOOKUP] Chicago, Ill
Practicing medicine is increasingly a matter of balancing risks and benefits of interventions, whether that intervention is a medication, a test, or a procedure. Each has a risk, just as failure to do each has a risk. The capable physician must be able to articulate these risks and benefits to the patient and then make reasonable recommendations. In an article that provides very important data about fetal thyroid function in women with Graves' disease, Nachum et al1 recommend umbilical blood sampling (UBS) for all women with Graves' disease who also have a “high” maternal thyroid-stimulating antibody (TSAb) level or when fetal signs of hyperthyroidism (intrauterine growth restriction [IUGR], goiter, cardiomegaly, or tachycardia) are found. Is this a reasonable recommendation? Do their data support this recommendation?
The authors followed up 26 fetuses (18 women) with Graves' disease over 10 years. There were five fetuses with abnormal thyroid function: three hypothyroid and two hyperthyroid. Their recommendation for UBS is based on these five fetuses. Could these five fetuses have been identified by clinical parameters? The answer is yes. Both hyperthyroid fetuses were born to mothers who were treated with iodine 131 before pregnancy, and both had high TSAb levels (>249%). Two of the three hypothyroid fetuses had fetal tachycardia and high TSAb levels (>460%) and were born to the same mother. Thus, just one fetus with hypothyroidism would have been missed if the authors had reserved UBS for pregnancies in which there was either a history of treatment with radioactive iodine and a high TSAB level or current evidence of fetal hyperthyroidism. In the one missed hypothyroid fetus, reduction and ultimately cessation of maternal treatment with propylthiouracil (PTU) corrected the fetal hypothyroidism. The authors present no data about this mother's thyroid function, but it can be assumed that the maternal free thyroxine index (FTI) was normal even after the PTU was discontinued, suggesting that the PTU dose should have been decreased regardless of the thyroid status of the fetus. The development of fetal hypothyroidism could probably have been avoided had the maternal PTU treatment been strictly titrated to the lowest possible dose to maintain the maternal FTI in the high normal range.
I agree with the recommendation to offer UBS and appropriate prenatal treatment to mothers with Graves' disease when there is evidence of fetal involvement (goiter, IUGR, fetal tachycardia). Three of four fetuses who met this criterion had abnormal thyroid function. However, the recommendation to offer an invasive procedure with fetal risks to all patients with a “high” TSAb level is not supported by these data. Only one of nine women with an isolated “high” TSAb level had a baby with hypothyroidism, the one who was corrected by cessation of PTU. Although the authors reported no risks of UBS in their series, the standard risk of fetal loss for UBS is 1% to 2%.2
The remaining question is whether all women with Graves' disease should be tested for the presence of TSAb in pregnancy. The current standard of care in the United States does not require TSAb screening for women with a history of Graves' disease.3 The data presented by Nachum et al indicate that there are insufficient data to support UBS for women with isolated “high” TSAb levels, which in turn means that there is no reason to perform TSAb testing routinely. Rather, TSAb should be reserved for women at significant risk for fetal thyroid dysfunction: women with a history of 131I treatment and women with a previously affected neonate. Finally, what is “high” TSAb? Nachum et al used >160% or >10 IU, but in the one ill fetus with no other identifiers the TSAb value was 250%. A recent study found that a threshold of >5 IU had a sensitivity of 100% and a specificity of 76% for neonatal thyrotoxicosis.4 In this study, five of six babies with neonatal thyrotoxicosis displayed fetal tachycardia; in the one case without fetal symptoms, the mother had a previously affected neonate. The maternal history would have identified this fetus at risk for thyrotoxicosis.
Practical recommendations based on available data are as follows:
TSAb should be done on women with history of treatment with 131I or with a previously affected neonate. UBS should be offered to pregnant women with Graves' disease if any one of the following are present: (a) a history of a prior affected baby, (b) a history of maternal 131I treatment and a high TSAb level (>5 IU or >160%), (c) the fetus displays fetal tachycardia, growth restriction,
fetal goiter, hydrops, or cardiomegaly. PTU treatment should be actively titrated to the lowest possible dose to maintain maternal FTI in the high normal range. Infants born to mothers with Graves' disease should be closely followed up by a pediatrician for thyroid dysfunction.
-- Cada vez que logro ver mis incontables imperfecciones y defectos me llego a sentir menos imperfecto
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