Relationship Between Birth Defects And Antithyroid Drugs In Early Pregnancy
Antithyroid drugs are the treatment mainstay of hyperthyroidism during pregnancy, but potential teratogenic effects have been reported. All ATDs, including propylthiouracil , methimazole and carbimazole , are equally effective in controlling hyperthyroidism during pregnancy. However, they cross the placenta and may cause problems, particularly during first-trimester organogenesis. In 2009, the concern of a rare but fatal PTU-induced hepatotoxicity was raised.45,46) The U.S. Food and Drug Administration and the ATA recommended PTU use only in the 1st trimester, to be switched to MMI by the 2nd trimester.5,47) However, this recommendation has potential side effects from both drugs.
A Danish nationwide study was conducted to determine the degree to which the use of ATD in early pregnancy is associated with an increased prevalence of birth defects.48) Andersen et al.48) reported that all ATDs were significantly associated with birth defects . Both were associated with urinary system malformation and PTU with malformations in the face and neck region. Omphalocele, omphalomesenteric duct anomalies, and MMI embryopathy were common in MMI/CMZ-exposed children.
- Conflicts of Interest
How Do Doctors Treat Postpartum Thyroiditis
The hyperthyroid stage of postpartum thyroiditis rarely needs treatment. If your symptoms are bothering you, your doctor may prescribe a beta-blocker, a medicine that slows your heart rate. Antithyroid medicines are not useful in postpartum thyroiditis, but if you have Graves disease, it may worsen after your baby is born and you may need antithyroid medicines.
Youre more likely to have symptoms during the hypothyroid stage. Your doctor may prescribe thyroid hormone medicine to help with your symptoms. If your hypothyroidism doesnt go away, you will need to take thyroid hormone medicine for the rest of your life.
Guidelines For Thyroid Disease In Pregnancy: Key Points
Sandra A. Fryhofer, MD
Hello. I’m Dr. Sandra Fryhofer. Welcome to Medicine Matters. The topic is the new guidelines on hypothyroidism during pregnancy, from the American Thyroid Association and published in the journal Thyroid. Here is why it matters.
Being pregnant can be a stress test for the thyroid. The size of the gland increases by 10%. Production of thyroid hormones T3 and T4 increases by about 50%. As a result, the normal thyroid-stimulating hormone level during pregnancy is lower than the normal nonpregnancy level.
Recommendations for Testing for Thyroid Disease During Pregnancy
The new recommendations for TSH levels during pregnancy are the following:
First trimester: less than 2.5 with a range of 0.1-2.5
Second trimester: 0.2-3.0
Third trimester: 0.3-3.0.
If the TSH is greater than 2.5 at any time during pregnancy, T4 levels should be checked to determine whether the hypothyroidism is overt or subclinical.
If T4 is low, the diagnosis is overt hypothyroidism, which can impair the infant’s neurocognitive development. There are also increased risks for premature birth, low birthweight, and miscarriage. Overt hypothyroidism must be treated.
Treatment is necessary when TSH is 10 or more, regardless of the T4 level. In addition, TSH should be monitored every 4 weeks during the first 20 weeks of gestation, then once again between 26 and 32 weeks.
Conception in Women With Hypothyroidism
Medications Recommended During Pregnancy
Thyroid Dysfunction And Reproductive Health
Thyroid function is regulated by the hypothalamus-pituitary axis , an interconnected duo made up of the hypothalamus and the pituitary gland . This pair is as thick as thieves when one of these organs sends a signal, it sets off a chain reaction in the other.
Because the HPA also controls the production of some of the most important hormones related to fertility, thyroid dysfunction can impact how much of those hormones are released. When any of these deviations from the status quo happen, they can disrupt menstrual cycles. Without the complete cycle, including ovulation, fertilization, and implantation, you cant get pregnant naturally.
As a result of these hormone changes, both hyperthyroidism and hypothyroidism have been linked to abnormal menstrual cycles.
All that said, getting a handle on your thyroid through treatment can reduce the chances of related fertility issues down the line. In one study of a group of almost 400 women suffering from infertility, 24% of participants were found to have hypothyroidism but within a year of treatment, 76% were able to conceive.
Patterns Of Thyroid Tests Associated With Thyroid Disease
Primary Hypothyroidism A high TSH and low thyroid hormone level can indicate primary hypothyroidism. Primary hypothyroidism occurs when the thyroid gland makes too little thyroid hormone. Symptoms of hypothyroidism can include feeling cold, constipation, weight gain, slowed thinking, and decreased energy. Causes of primary hypothyroidism include:
- Autoimmune thyroid disease, including Hashimoto’s thyroiditis
- Thyroid gland dysfunction due to a medication
- Removal of all or part of the thyroid gland
- Radiation injury to the thyroid
- Excess treatment with anti-thyroid medications
Early or mild hypothyroidism may present as a persistently elevated TSH and a normal FT4 hormone level. This pattern is called subclinical hypothyroidism and your doctor may recommend treatment. Over time, untreated subclinical hypothyroidism can contribute to heart disease.
It is important to remember that normal TSH levels in older individuals are higher than the normal ranges for younger individuals.
Primary Hyperthyroidism A low TSH and a high thyroid hormone level can indicate primary hyperthyroidism. Primary hyperthyroidism occurs when the thyroid gland makes or releases too much thyroid hormone. Symptoms of hyperthyroidism can include tremors, palpitations, restlessness, feeling too warm, frequent bowel movements, disrupted sleep, and unintentional weight loss. Causes of primary hyperthyroidism include:
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What Tests Are Used To Check Thyroid Function
- with symptoms of thyroid dysfunction
- with their own or family history of thyroid disease
- with previous thyroid surgery
- who are severely overweight or obese
- who are aged 30 or older
If you feel you fit into one or more of the above categories, ask your doctor or midwife if your thyroid function should be checked.
How Can Hypothyroidism Affect Pregnancy
Untreated hypothyroidism during pregnancy is linked to problems for women and babies during pregnancy and after birth.
Problems for women can include:
- Anemia. This is when you dont have enough healthy red blood cells to carry oxygen to the rest of your body.
- Gestational hypertension.This is high blood pressure that starts after 20 weeks of pregnancy and goes away after you give birth.
- Placental abruption
- Postpartum hemorrhage . This when a woman has heavy bleeding after giving birth. Its a serious but rare condition. It usually happens within 1 day of giving birth, but it can happen up to 12 weeks after having a baby.
- Myxedema, a rare condition caused by severe, untreated hypothyroidism that can cause you to go into a coma and can cause death
- Heart failure. This is when your heart doesnt pump blood as well as it should. Heart failure cause by hypothyroidism is rare.
Problems for babies can include:
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What Is The Interaction Between The Thyroid Function Of The Mother And The Baby
For the first 18-20 weeks of pregnancy, the baby is completely dependent on the mother for the production of thyroid hormone. By mid-pregnancy, the babys thyroid begins to produce thyroid hormone on its own. The baby, however, remains dependent on the mother for ingestion of adequate amounts of iodine, which is essential to make the thyroid hormones. The World Health Organization recommends iodine intake of 250 micrograms/day during pregnancy to maintain adequate thyroid hormone production. Because iodine intakes in pregnancy are currently low in the United States, the ATA recommends that US women who are planning pregnancy, pregnant, or breastfeeding should take a daily supplement containing 150 mcg of iodine.
Who Should Be Tested
Anyone with the symptoms of an overactive or underactive thyroid or postpartum depression should have a TSH test to tell whether thyroid levels are normal. Thyroid hormone levels do not need to be checked unless the TSH is high or low .
Since the symptoms of a change in thyroid function may be so mild as to be missed or mistaken for other health problems, your doctor may also choose to check your TSH level about two to four months after delivery if you or a close relative have ever had a thyroid problem. You may also have a TSH test after pregnancy if your doctor suspects that you are at increased risk for thyroid dysfunction. This could be your situation if you or close relatives have other disorders or physical traits suggesting an increased risk for thyroid problems. These include juvenile diabetes, rheumatoid arthritis, pernicious anemia due to a lack of vitamin B12, colitis, and prematurely gray hair. There is even new research which suggests that if you or a close relative are either left-handed or ambidextrous you may have an increased risk for thyroid dysfunction and other immune problems.
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What Are The Symptoms Of Hypothyroidism
Hypothyroidism is a common condition. It can go undetected if symptoms are mild. Hypothyroidism means the thyroid is underactive and making insufficient amounts of thyroid hormones. Symptoms of hypothyroidism may be mild and may start slowly. The following are the most common symptoms of hypothyroidism:
Unable to stand cold temperatures
Skin and hair changes, including dry skin and loss of eyebrows
Carpal tunnel syndrome
Slow heart rate
Irregular menstrual periods
The symptoms of hypothyroidism may resemble other conditions or medical problems. Always talk with your healthcare provider for a diagnosis.
Who Do I Contact If I Have Any Questions
If you have any questions, you should discuss them with your GP or your midwife. They can advise you, or contact the hospital on your behalf.
For patient support groups and further information, please look at the;British Thyroid Foundation website.
This information is intended for patients receiving care in Brighton & Hove or Haywards Heath.
The information in this leaflet is for guidance purposes only and is in no way intended to replace professional clinical advice by a qualified practitioner.
Publication Date: July 2021
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Normal Thyroid Levels For Tsh
Thyroid function is measure base of the TSH range of TSH blood test. The normal thyroid levels for TSH used to be from 0.5 to 5.0. After clinical studies, in 2003, the TSH range has been revised to 0.3 – 3.0 as normal TSH levels.
If you are trying to conceive, a normal level of TSH for conception should be lower than 2, that is what many reproductive endocrinologists prefer to see. Hypothyroidism is present when elevated TSH levels are present.
Normal Thyroid Levels for T4
Total T4 levels should be approximately 4.5 to 12.5. A low T4 level with High TSH indicates hypothyroidism. Free T4 normal range is approximately 0.7 to 2.0. If the value is low, it indicates f hypothyroidism.
Normal Thyroid Levels for T3
Total T3 levels should be approximately 80 to 220. Hypothyroidism is suspected when values are less than 80, while hyperthyroidism if over 220. Free T3 levels should be approximately 2.3 to 4.2. When values are less than 2.3, hypothyroidism is most likely.
Continuation Of Thyroid Hormone Therapy Post Partum
Thyroid hormone therapy was continued during the first year post partum for 2252 of the 5050 deliveries with initiation of such therapy during the pregnancy . Among the 1903 deliveries with initiation of thyroid hormone therapy during the pregnancy and highest TSH between 0.10 and 4.00 mIU/L, the therapy was continued post partum for 691 . For levothyroxine started in pregnancy and continued post partum, the median dosage was 50 g/day. For levothyroxine started in pregnancy and stopped post partum, the median dosage prescribed in pregnancy was 25 g/day. In the postpartum period, TSH was 10.00 mIU/L or higher for only 5 women who started thyroid hormone therapy in pregnancy and continued post partum. A sensitivity analysis with filling of 2 or more prescriptions for thyroid hormone in the first year post partum also showed that treatment was commonly continued post partum .
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What Are Signs And Symptoms Of Hyperthyroidism
Hyperthyroidism thats untreated or not treated correctly is linked to problems for women and babies during pregnancy and after birth.
Problems for women can include:
- Preeclampsia. This is a serious blood pressure condition that can happen after the 20th week of pregnancy or after giving birth . Its when a woman has high blood pressure and signs that some of her organs, like her kidneys and liver, may not be working normally. Blood pressure is the force of blood that pushes against the walls of your arteries. Arteries are blood vessels that carry blood away from your heart to other parts of the body. High blood pressure is when the force of blood against the walls of the blood vessels is too high. It can stress your heart and cause problems during pregnancy.
- Pulmonary hypertension. This is a kind of high blood pressure that happens in the arteries in your lungs and on the right side of your heart.
- Placental abruption. This is a serious condition in which the placenta separates from the wall of the uterus before birth. The placenta grows in your uterus and supplies the baby with food and oxygen through the umbilical cord.
- Heart failure. This is when your heart cant pump enough blood to the rest of your body.
- Thyroid storm. This is when your symptoms suddenly get much worse. Its a rare, but life-threatening condition during pregnancy. Pregnant women who have thyroid storm are at high risk of heart failure.
Problems for babies can include:
Normal Thyroid Levels During Pregnancy
During a normal pregnancy, the thyroid TSH levels should be as follow. These value apply to those that do not present autoimmune antibodies and have sufficient levels of iodine.
Normal TSH Levels during the first three months of pregnancy: 0.24 – 2.99. Normal TSH Levels during the second trimester of pregnancy: 0.46-2.95. Normal TSH Levels during the last three months of pregnancy: 0.43 – 2.78.
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How Can You Avoid The Complications Of Hypothyroidism In Pregnancy
A number of medical associations and organizations have made recommendations on screening for thyroid disease. Some of the recommendations are:
The management of each womans situation is considered individually after consultation with her physician. The benefits of treatment extend not only to pregnant women with hypothyroidism, but also to their children.
Is This A Permanent Condition
For most women it is a temporary condition. It is important to allow your doctor to continue to monitor your thyroid levels during treatment. Eventually, the doctor may be able to taper off your medication as your thyroid returns to normal functioning levels. Eighty percent of patients should eventually be able to be taken off medication. Those with positive thyroid antibodies are more likely to continue in the hypothyroid phase and would need lifelong thyroid hormone replacement.
Last reviewed by a Cleveland Clinic medical professional on 10/23/2020.
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What Should I Eat During Pregnancy To Help Keep My Thyroid And My Babys Thyroid Working Well
Because the thyroid uses iodine to make thyroid hormone, iodine is an important mineral for you while youre pregnant. During pregnancy, your baby gets iodine from your diet. Youll need more iodine when youre pregnantabout 250 micrograms a day.1 Good sources of iodine are dairy foods, seafood, eggs, meat, poultry, and iodized saltsalt with added iodine. Experts recommend taking a prenatal vitamin with 150 micrograms of iodine to make sure youre getting enough, especially if you dont use iodized salt.1 You also need more iodine while youre breastfeeding since your baby gets iodine from breast milk. However, too much iodine from supplements such as seaweed can cause thyroid problems. Talk with your doctor about an eating plan thats right for you and what supplements you should take. Learn more about a healthy diet and nutrition during pregnancy.
Eat Healthy And On Time:
Eat natural, home-cooked food. Avoid eating out. Stay away from prepackaged and processed foods. Try to eat as much organic food as possible. Wash your fruits and vegetables in vinegar bath before consumption. You need to eat on time, whether you have hypothyroidism or not and whether you are pregnant or not. But you absolutely need to eat on time to regulate your metabolism if you are both hypothyroid and pregnant. On the whole, eat fresh, clean and healthy food every day
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Is It Necessary To Perform Thyroid Hormone Tests In All Pregnant Women
Guidelines on this matter vary among expert groups. In Korea, obstetricians do not perform routine thyroid hormone tests in pregnant women. The KTA recommends the following ambiguous suggestions: 1) There is insufficient evidence to recommend for or against routine TSH screening in early pregnancy; 2) TSH measurement in early pregnancy is performed in high-risk pregnant women, although there is insufficient evidence to recommend for or against the pre-pregnancy TSH test; 3) Routine free T4 measurement during pregnancy is not recommended; and 4) There is insufficient evidence to recommend for or against routine TPOAb screening in early pregnancy.11) In conclusion, the KTA recommends only serum TSH measurement in early pregnancy and only in high-risk pregnant women. High-risk refers to a history of hyperthyroidism or hypothyroidism; current symptoms/signs of thyroid dysfunction; TPOAb positivity; presence of a goiter; history of head or neck radiation or prior thyroid surgery; age >30 years; type 1 diabetes or other autoimmune disorder; history of pregnancy loss, preterm delivery, or infertility; family history of autoimmune thyroid disease or thyroid dysfunction; morbid obesity ; use of amiodarone or lithium or recent administration of iodinated radiologic contrast; and residing in an area of known moderate to severe iodine insufficiency.