Feeling tired, moody, achy and forgetful? Are you gaining weight, breaking out and swelling up? Of course you are; you’re pregnant! While these symptoms are common among pregnant women, they can rarely also signs of a thyroid disorder. So how can your doctor tell the difference?
If you’ve never been diagnosed with a thyroid condition before but you’re experiencing the symptoms of one (and especially if you have a family history of thyroid disease), your doctor will run a simple blood test. Luckily, thyroid disorders can be treated safely with medication during pregnancy, minimizing any risks to you or your baby.
What is thyroid disorder?
The thyroid gland, located at the front of the neck just below the voice box, is part of the endocrine system, which produces all of the hormones in your body. The hormones your thyroid creates play a key role in regulating your metabolism — the way your body uses energy — along with your temperature, weight, cholesterol levels and other key body functions.
Production of thyroid hormones, in turn, is regulated by levels of thyroid-stimulating hormone (TSH), generated by your pituitary gland (in your brain). The levels of thyroid hormones in your blood naturally fluctuate throughout the day; usually, the pituitary gland responds by creating more or less TSH.
Hypothyroidism (too little thyroid hormone), can cause many of the body’s functions to slow down, or hyperthyroidism (too much thyroid hormone), can cause many of the body’s functions to speed up.
How does pregnancy affect thyroid levels?
When you’re expecting, two pregnancy hormones you’re probably pretty familiar with already — estrogen and human chorionic gonadotropin (hCG) — increase your thyroid hormone levels.
In the first trimester, hCG — which is similar to TSH — stimulates production of thyroid hormones. And throughout pregnancy, increased estrogen levels produce a hormone that helps transports thyroid hormones in the blood. By the third trimester, the thyroid’s volume may be 10-15 percent greater. All of this is normal.
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For both of the above reasons and because many symptoms of a normal pregnancy and a thyroid disorder (like fatigue) are similar, thyroid tests can be more difficult to interpret when you’re expecting.
And because thyroid hormones are crucial to the healthy development of your baby’s brain and nervous system — especially during the first trimester, before your baby’s thyroid has developed and he’s completely reliant on you for thyroid hormone — it’s all the more important to understand your risk factors and symptoms so you so can get treatment if you need it.
Hypothyroidism and pregnancy
Hypothyroidism is a deficiency of the thyroid hormone thyroxine due to an underactive thyroid gland. During pregnancy, the condition — which occurs in about two to three of every 500 expecting women — is usually caused by Hashimoto’s disease, an autoimmune disorder that causes chronic inflammation of the thyroid gland and interferes with its ability to produce hormones.
Women who have been diagnosed with hypothyroidism in the past and those who have a family history of thyroid disorders have the highest risk of experiencing the condition during pregnancy.
Your thyroid hormones are critical to normal development of the baby’s brain and nervous system — which means babies who don’t get enough of these hormones in the first trimester, when they’re dependent on the mother’s supply, can be born with neurological development problems.
Symptoms of hypothyroidism in pregnancy
Do any of the following sound familiar? While common in pregnancy, it’s still best to play it safe and mention them to your doctor:
- Extreme fatigue
- Feeling cold
- Memory loss
- Muscle aches and cramps
- Higher than average weight gain
- Skin problems
- Hair loss
- Swelling (especially of the hands and feet)
- Constipation
Hypothyroidism risks during pregnancy
If left untreated, hypothyroidism during pregnancy can lead to:
- Premature birth
- Preeclampsia (a severe increase in blood pressure)
- Miscarriage
- Low birth weight
- Anemia for the mother
- Stillbirth
- Rarely, congestive heart failure for the mother
Your doctor will discuss the symptoms you’ve been experiencing and then run a blood test to check for levels of TSH and T4 (a thyroid hormone).
Hypothyroidism treatment during pregnancy
Your doctor will prescribe a synthetic hormone called levothyroxine — which is not only safe during pregnancy, it’s vital to both you and your baby. Work with your endocrinologist and obstetrician to determine the right dose for you. If you had preexisting hypothyroidism, they will likely need to increase your levels, since the body requires more thyroid hormones when it’s in baby-growing mode.
During pregnancy and postpartum, your thyroid hormone levels will be monitored every six to eight weeks to see if your dose needs further adjustment.
In addition to medication, be sure to eat a healthy balanced diet and take a prenatal vitamin. Most likely your doctor will also suggest a supplement of 150 micrograms (mcg) iodine a day during pregnancy (if there’s not already that much in your prenatal vitamin), since iodine is important for thyroid health. You’ll also find iodine in seafood and iodized salt, so opt for that over sea salt.
Hyperthyroidism and pregnancy
Hyperthyroidism is when an overactive gland produces too much thyroid hormone. The condition occurs in about one to four of every 1,000 pregnancies, according to the National Institutes of Health.
Hyperthyroidism is usually caused by Graves' disease (an autoimmune disorder) in expecting moms, where the immune system makes an antibody called thyroid-stimulating immunoglobulin (TSI) that causes the thyroid to overproduce thyroid hormone. More rarely, hyperthyroidism during pregnancy is linked to hyperemesis gravidarum (severe nausea and vomiting), since both conditions are triggered by higher hCG levels.
Symptoms of hyperthyroidism in pregnancy
Call your doctor if you experience any of the following:
- Irregular or increased heartbeat
- Fatigue
- Nervousness
- Severe nausea or vomiting
- Trouble sleeping
- Weight loss or less weight gain than a “typical” pregnancy
The good news: If you had preexisting Graves Disease, you may actually see an improvement and even remission in symptoms in the second and third trimesters, since the body suppresses the immune system during pregnancy. And if your condition was linked to hyperemesis gravidarum, it will likely disappear along with nausea and vomiting in the second trimester due to lower levels of hCG.
Hyperthyroidism risks during pregnancy
As with hypothyroidism, untreated hyperthyroidism can lead to serious complications for both you and your baby, including:
- Congestive heart failure in the mother
- Preeclampsia
- Miscarriage
- Premature birth
- Low birth weight
Your practitioner will review your symptoms and run a blood test to check for TSH, T3 and T4 levels.
Hyperthyroidism treatment during pregnancy
If your condition is mild, you likely won’t need any treatment. More severe cases require antithyroid medications called propylthiouracil (PTU) in the lowest effective dose for the first trimester.
After the first trimester, if necessary, your doctor may switch you to the antithyroid medication methimazole (Tapazole, Northyx). Either way, you’ll need to check in with your doctor regularly to make sure the medications and dose are still right for you.
In rare cases (if you don’t respond to medications or experience severe side effects), you may need surgery to remove part of the thyroid.
With hyperthyroidism, if the mother has specific antibodies that can stimulate the thyroid, then this may also affect baby's thyroid. Baby may have circulating antibodies for a few weeks after birth and in that case, will need extra monitoring.
Bottom line? The body’s need for thyroid hormone fluctuates during pregnancy. So if you’ve ever been diagnosed with any thyroid problems in the past or currently take medication for a thyroid condition, be sure to let your practitioner know. It’s possible you may require medication again or need to adjust your dose.
Also be aware that after pregnancy, many of the symptoms of a thyroid disorder can be similar to those of postpartum depression (PPD). So if you’re experiencing any of the above symptoms, be sure to let your doctor know so you can receive a diagnosis and get the treatment you need.
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