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Hyperthyroidism and Pregnancy
Mar 17, 2008 01:17AM
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Hyperthyroidism and Pregnancy
Hyperthyroidism affects less than 1% of all pregnancies, but it has important consequences for both the mother and fetus. Although many women with hyperthyroidism experience changes in their menstrual cycle, such as irregular periods and lack of ovulation, these changes do not necessarily into infertility problems in a women with only mild hyperthyroidism. However, once a woman with hyperthyroidism becomes pregnant, there is an increased risk of miscarriage, spontaneous abortion, fetal growth retardation, premature labor and delivery, congenital malformations and possibly pre-eclampsia. Fetal death may occur as a result of chromosomal abnormalities such as Down's syndrome. These risks are decreased in women where the hyperthyroidism is recognized early and treated appropriately.
Diagnosis
Often it is difficult to distinguish the symptoms of hyperthyroidism from those of normal pregnancy. The symptoms of both conditions may overlap. For example, feeling hot, excessive sweating, emotional excitement, nervousness, vomiting or a racing heart beat may be common to both normal pregnancy as well as hyperthyroidism. However, two common symptoms exclusive to hyperthyroidism are: a very rapid heart rate above 100 beats per minute, and weight loss. If you are pregnant and are experiencing these symptoms, you should be tested for hyperthyroidism so that it can be treated in order to prevent problems with your pregnancy.
Once the diagnosis of hyperthyroidism has been made, it is important to determine the cause of your overactive thyroid in order to choose the most effective treatment. (see the section on hyperthyroidism.) It is important to note that the cause must be diagnosed from physical exam and blood tests. Nuclear scanning can not be performed if you are pregnant because it uses radioactive materials that are taken up by the thyroid gland of both the mother and fetus. The fetal thyroid can be destroyed by this radioactive material, resulting in an underactive thyroid gland, which can cause severe mental, as well as physical, retardation. Always tell your physician if you are pregnant or think you might be pregnant in order to avoid tests that are potentially harmful to your baby.
One type of blood test called thyroid-stimulating immunoglobulins may be elevated if you have a particular type of hyperthyroidism called Graves' disease (see the section on hyperthyroidism). This test may be elevated even if you are not currently experiencing any symptoms of hyperthyroidism. It is important to follow these levels of thyroid-stimulating immunoglobulins with blood tests every few months if you are pregnant because elevated levels may have a profound effect on the newborn baby (see section on newborn hyperthyroidism below).
Treatment
Hyperthyroidism may affect the mother as well as the developing fetus. The most serious complication from untreated hyperthyroidism is heart disease, specifically heart failure as a result of the heart beating faster than normal and working overtime in response to the increased levels of thyroid hormone. Patients may potentially develop a more serious complication of untreated hyperthyroidism called thyroid storm. Usually a stressful triggering event such as labor, caesarean section or untreated infection can cause the hyperthyroidism to spiral out of control. This excess of thyroid hormone can cause death if not diagnosed and treated promptly.
Many of the treatments that are typically used for hyperthyroidism can be harmful to the developing fetus or can be passed to the newborn baby via the breast milk. For example, beta blockers (to control heart rate) and iodides can not be used because they may cause problems with your placenta, growth retardation of the fetus or an underactive fetal thyroid. Therefore these drugs are only used in extreme circumstances when the mother's life is in danger or when thyroid surgery is required. Radioactive iodine also can not be used because the radioactive iodine may destroy the fetal thyroid as well as the mother's thyroid gland, resulting in a hypothyroid baby. In this case, not only is the baby at risk for intellectual and physical growth retardation, but the hypothyroidism may cause severe enlargement of the baby's thyroid gland. The gland may be so large that it interferes with normal vaginal delivery, necessitating caesarean section. Therefore, the goal for the treatment of hyperthyroid women is twofold 1) to protect the mother and 2) to protect the developing fetus.
Propylthiouracil (PTU) is the most commonly used drug to treat hyperthyroidism during pregnancy. However, it is important to note that the fetal thyroid is vulnerable to anti-thyroid medications taken by the mother such as methimazole, PTU or radioactive iodine. If the fetal thyroid is affected by these medications, the developing baby may not produce enough thyroid hormone to sustain normal development. However, the risk of harm to the fetus is minimal if the mother is given the lowest possible dose necessary (which is often all that is needed since pregnancy itself can often improve the course of Graves' disease due to natural suppression of the mother's immune system during this period). Without treatment, the baby is at risk for spontaneous abortion and premature delivery. Therefore, the risks and benefits of each individual situation must be carefully measured whenever starting drug therapy in a pregnant woman. No long term ill effects have been noted in intellectual development of those children born to mothers taking PTU for hyperthyroidism during their pregnancy.
Surgery
Surgery is reserved for those pregnant women who can not take anti-thyroid medication, for example due to allergy or if the mother requires very high doses to control the disease. Thyroid surgery may be performed safely during pregnancy if you are properly prepared with anti-thyroid drugs in order to avoid "thyroid storm" (see above). The safest time to operate is during the second trimester because the risks of miscarriage (during the first trimester) or premature labor and delivery (third trimester) are minimized.
Effects on Your Baby
Even if you are taking the appropriate medicine during your pregnancy to successfully treat your hyperthyroidism, your baby is still at risk for the development of hyperthyroidism called neonatal thyrotoxicosis. Even with proper medication or surgery, thyroid stimulating antibodies may remain in your bloodstream and may be passed to your newborn baby. Therefore, your baby must be tested (with a simple blood test) immediately after birth for a possible overactive thyroid gland.
In addition, anti-thyroid drugs taken by you during your pregnancy may pass through the bloodstream and placenta to your baby and mask your newborn baby's hyperthyroidism for 7 to 10 days until these medications have worn off. Careful follow-up by the baby's pediatrician is essential. Although less than 2% of babies who are born to mothers with Graves' disease suffer from newborn hyperthyroidism, the mortality rate of this disease if not recognized and properly treated is as high as 20%.
Both of the commonly used anti-thyroid drugs, methimazole and PTU are passed through the breast milk into your new born baby. In high doses, these medications may block the baby's thyroid gland, causing hypothyroidism. This underactive thyroid may result in severe intellectual and growth retardation. PTU passes into the breast milk less readily than methimazole does, and therefore PTU is preferred in mothers who are breast feeding. However, because of the risk of hypothyroidism for the baby, only mothers who are on extremely low doses of PTU should be allowed to breast feed. The children of these mothers should be followed closely by their pediatricians. If the dose of PTU needs to be increased, the mothers should bottle feed rather than nurse their baby.
Hyperthyroidism affects less than 1% of all pregnancies, but it has important consequences for both the mother and fetus. Although many women with hyperthyroidism experience changes in their menstrual cycle, such as irregular periods and lack of ovulation, these changes do not necessarily into infertility problems in a women with only mild hyperthyroidism. However, once a woman with hyperthyroidism becomes pregnant, there is an increased risk of miscarriage, spontaneous abortion, fetal growth retardation, premature labor and delivery, congenital malformations and possibly pre-eclampsia. Fetal death may occur as a result of chromosomal abnormalities such as Down's syndrome. These risks are decreased in women where the hyperthyroidism is recognized early and treated appropriately.
Diagnosis
Often it is difficult to distinguish the symptoms of hyperthyroidism from those of normal pregnancy. The symptoms of both conditions may overlap. For example, feeling hot, excessive sweating, emotional excitement, nervousness, vomiting or a racing heart beat may be common to both normal pregnancy as well as hyperthyroidism. However, two common symptoms exclusive to hyperthyroidism are: a very rapid heart rate above 100 beats per minute, and weight loss. If you are pregnant and are experiencing these symptoms, you should be tested for hyperthyroidism so that it can be treated in order to prevent problems with your pregnancy.
Once the diagnosis of hyperthyroidism has been made, it is important to determine the cause of your overactive thyroid in order to choose the most effective treatment. (see the section on hyperthyroidism.) It is important to note that the cause must be diagnosed from physical exam and blood tests. Nuclear scanning can not be performed if you are pregnant because it uses radioactive materials that are taken up by the thyroid gland of both the mother and fetus. The fetal thyroid can be destroyed by this radioactive material, resulting in an underactive thyroid gland, which can cause severe mental, as well as physical, retardation. Always tell your physician if you are pregnant or think you might be pregnant in order to avoid tests that are potentially harmful to your baby.
One type of blood test called thyroid-stimulating immunoglobulins may be elevated if you have a particular type of hyperthyroidism called Graves' disease (see the section on hyperthyroidism). This test may be elevated even if you are not currently experiencing any symptoms of hyperthyroidism. It is important to follow these levels of thyroid-stimulating immunoglobulins with blood tests every few months if you are pregnant because elevated levels may have a profound effect on the newborn baby (see section on newborn hyperthyroidism below).
Treatment
Hyperthyroidism may affect the mother as well as the developing fetus. The most serious complication from untreated hyperthyroidism is heart disease, specifically heart failure as a result of the heart beating faster than normal and working overtime in response to the increased levels of thyroid hormone. Patients may potentially develop a more serious complication of untreated hyperthyroidism called thyroid storm. Usually a stressful triggering event such as labor, caesarean section or untreated infection can cause the hyperthyroidism to spiral out of control. This excess of thyroid hormone can cause death if not diagnosed and treated promptly.
Many of the treatments that are typically used for hyperthyroidism can be harmful to the developing fetus or can be passed to the newborn baby via the breast milk. For example, beta blockers (to control heart rate) and iodides can not be used because they may cause problems with your placenta, growth retardation of the fetus or an underactive fetal thyroid. Therefore these drugs are only used in extreme circumstances when the mother's life is in danger or when thyroid surgery is required. Radioactive iodine also can not be used because the radioactive iodine may destroy the fetal thyroid as well as the mother's thyroid gland, resulting in a hypothyroid baby. In this case, not only is the baby at risk for intellectual and physical growth retardation, but the hypothyroidism may cause severe enlargement of the baby's thyroid gland. The gland may be so large that it interferes with normal vaginal delivery, necessitating caesarean section. Therefore, the goal for the treatment of hyperthyroid women is twofold 1) to protect the mother and 2) to protect the developing fetus.
Propylthiouracil (PTU) is the most commonly used drug to treat hyperthyroidism during pregnancy. However, it is important to note that the fetal thyroid is vulnerable to anti-thyroid medications taken by the mother such as methimazole, PTU or radioactive iodine. If the fetal thyroid is affected by these medications, the developing baby may not produce enough thyroid hormone to sustain normal development. However, the risk of harm to the fetus is minimal if the mother is given the lowest possible dose necessary (which is often all that is needed since pregnancy itself can often improve the course of Graves' disease due to natural suppression of the mother's immune system during this period). Without treatment, the baby is at risk for spontaneous abortion and premature delivery. Therefore, the risks and benefits of each individual situation must be carefully measured whenever starting drug therapy in a pregnant woman. No long term ill effects have been noted in intellectual development of those children born to mothers taking PTU for hyperthyroidism during their pregnancy.
Surgery
Surgery is reserved for those pregnant women who can not take anti-thyroid medication, for example due to allergy or if the mother requires very high doses to control the disease. Thyroid surgery may be performed safely during pregnancy if you are properly prepared with anti-thyroid drugs in order to avoid "thyroid storm" (see above). The safest time to operate is during the second trimester because the risks of miscarriage (during the first trimester) or premature labor and delivery (third trimester) are minimized.
Effects on Your Baby
Even if you are taking the appropriate medicine during your pregnancy to successfully treat your hyperthyroidism, your baby is still at risk for the development of hyperthyroidism called neonatal thyrotoxicosis. Even with proper medication or surgery, thyroid stimulating antibodies may remain in your bloodstream and may be passed to your newborn baby. Therefore, your baby must be tested (with a simple blood test) immediately after birth for a possible overactive thyroid gland.
In addition, anti-thyroid drugs taken by you during your pregnancy may pass through the bloodstream and placenta to your baby and mask your newborn baby's hyperthyroidism for 7 to 10 days until these medications have worn off. Careful follow-up by the baby's pediatrician is essential. Although less than 2% of babies who are born to mothers with Graves' disease suffer from newborn hyperthyroidism, the mortality rate of this disease if not recognized and properly treated is as high as 20%.
Both of the commonly used anti-thyroid drugs, methimazole and PTU are passed through the breast milk into your new born baby. In high doses, these medications may block the baby's thyroid gland, causing hypothyroidism. This underactive thyroid may result in severe intellectual and growth retardation. PTU passes into the breast milk less readily than methimazole does, and therefore PTU is preferred in mothers who are breast feeding. However, because of the risk of hypothyroidism for the baby, only mothers who are on extremely low doses of PTU should be allowed to breast feed. The children of these mothers should be followed closely by their pediatricians. If the dose of PTU needs to be increased, the mothers should bottle feed rather than nurse their baby.