Postpartum Thyroiditis and Related Issues After Pregnancy

Your thyroid function may be altered after having a baby

It's common for women to feel tired, experience mood swings, and have a variety of other symptoms in the months after childbirth. But for some women, symptoms can become troublesome and may point to a thyroid problem known as postpartum thyroiditis (PPT)—an inflammation of the thyroid that initially occurs in the first year after childbirth, miscarriage, or induced abortion. It's considered a variation of autoimmune thyroiditis, also known as Hashimoto's thyroiditis.

Types of PPT

There are several types of postpartum thyroiditis, including:

  • Classic: You go through a period of temporary thyrotoxicosis—a condition characterized by having too much thyroid hormone in your system—followed by a period of temporary hypothyroidism, going back to normal thyroid function by the end of the first year. This occurs in about 25 percent of women with PPT.
  • Isolated thyrotoxicosis: You have a period of hyperthyroidism, but not hypothyroidism, and the hyperthyroidism eventually resolves itself. This usually starts between two and six months after giving birth and also occurs in around 25 percent of women with PPT.
  • Isolated hypothyroidism: The other half of PPT patients develop an underactive thyroid between three to 12 months after giving birth. Though this resolves in the majority of cases, 10 percent to 20 percent of women develop permanent hypothyroidism.

Risk Factors

The condition is fairly common, as it's estimated that approximately 7 percent to 8 percent of women who have been pregnant develop it.

Certain risk factors may help predict who is at an increased risk for developing postpartum thyroiditis. These include:

  • A personal or family history thyroid dysfunction
  • A history of PPT (you have a 70 percent chance of developing it again in each subsequent pregnancy)
  • The presence of antithyroid antibodies prior to pregnancy: Changes in the immune system during pregnancy may make the symptoms of thyroiditis more severe. Up to 50 percent of women with elevated antithyroid antibodies develop postpartum thyroiditis.
  • Positive pituitary antibodies
  • Type 1 diabetes: Up to 25 percent of women with type 1 diabetes develop postpartum thyroiditis.
  • Lupus
  • Chronic viral hepatitis

Typical Course

The most common course for postpartum thyroiditis involves the onset of mild hypothyroidism starting from two to six months after your baby is born. The hypothyroidism then resolves as your thyroid normalizes.

The next most common presentation is mild hyperthyroidism, which begins one to four months after delivery, after which your thyroid normalizes.

A third course is characterized by mild hyperthyroidism that then shifts into a period of mild hypothyroidism for several weeks to several months, followed by normalization of thyroid function. 

While some cases of postpartum thyroiditis resolve over time, there is a strong risk that the woman will continue to have a thyroid condition.

It's estimated that as many as half of women with postpartum thyroiditis will develop persistent hypothyroidism, a goiter (an enlarged thyroid gland), or both, within four to eight years of onset. This means that you should have your TSH level checked every year.

Symptoms

There are a number of symptoms of postpartum thyroiditis that may appear during both the hyperthyroid and hypothyroid phases of the condition. These include:

  • Decreased milk volume in breastfeeding women
  • Hair loss
  • Fatigue
  • Goiter that is painless
  • Depression, anxiety, and moodiness

Symptoms during the hyperthyroid phase of postpartum thyroiditis are usually milder versions of general hyperthyroidism symptoms. These symptoms may include anxiety, muscle weakness, irritability, heart palpitations, fast heartbeat, tremor, weight loss, and diarrhea.

Likewise, the symptoms during the hypothyroid phase of postpartum thyroiditis are milder versions of general hypothyroidism symptoms. They may include sluggishness, dry skin, difficulty losing weight (or weight gain), constipation, low body temperature, and puffiness in the eyes, face, and hands.

Diagnosis

Your doctor will typically run several blood tests to diagnose postpartum thyroiditis. In the hyperthyroid phase, your blood tests typically show a low thyroid-stimulating hormone (TSH), and high-normal or elevated thyroxine (T4) and triiodothyronine (T3).

In the hypothyroid phase, your TSH will be elevated, and T4 and T3 will be low or low-normal. Thyroid peroxidase (TPO) antibody levels are likely to be elevated in the majority of women with postpartum thyroiditis, especially during the hypothyroid phase.

In some cases of postpartum thyroiditis, an ultrasound is performed and will show enlargement of your thyroid gland.

It's important to note that along with postpartum thyroiditis, autoimmune Graves' disease (which causes hyperthyroidism) may occur after your baby is born. While postpartum thyroiditis is a far more common cause of hyperthyroidism, your doctor will want to ensure he does not miss a diagnosis of Graves' disease.

Some distinguishing factors of Graves' disease include more severe symptoms, more thyroid enlargement, and eye-related symptoms (called Graves' ophthalmopathy). 

In some cases, a radioiodine uptake test is done to differentiate postpartum thyroiditis from Graves' disease. Note, however, that this test is contraindicated if you're breastfeeding unless you pump and discard your milk for a few days afterward.




Hyperthyroid Treatment

Antithyroid drugs aren't recommended for the hyperthyroid period of postpartum thyroiditis. If you have symptoms, your doctor may prescribe a beta-blocker such as propranolol or metoprolol at the lowest possible dose for a few weeks to relieve them. Propranolol is preferred if you're breastfeeding since it doesn't transfer to the breastmilk as easily.

The American Thyroid Association (ATA) recommends that once your hyperthyroid phase subsides, your TSH level should be checked again after four to six weeks to screen for the hypothyroid phase, which occurs in about 75 percent of cases.

Hypothyroid Treatment

If you do end up in the hypothyroid phase of PPT, your treatment plan will depend on several factors. Here's what's generally recommended:

  • Synthroid (levothyroxine): If you have severe symptoms of hypothyroidism, you're breastfeeding, and/or you're trying to get pregnant again, your doctor will likely start you on levothyroxine. You will probably also be put on the drug if you have no symptoms but your TSH level is above 10 mIU/L. In cases where you only have mild hypothyroid symptoms, your doctor might think about putting you on levothyroxine, depending on your other circumstances such as TSH level and whether or not you're breastfeeding or trying to get pregnant.
  • Close monitoring: If you don't have any hypothyroid symptoms and your TSH level is under 10 mIU/L, you probably won't need treatment, but you'll need your TSH levels checked every four to eight weeks until your thyroid function goes back to normal.

Levothyroxine is typically prescribed for about a year and then gradually tapered off while closely monitoring your TSH levels to make sure you haven't developed permanent hypothyroidism. The exception to this is if you get pregnant or want to get pregnant during this time. In that case, your doctor will leave you on your medication until a later time.

Breastfeeding Considerations

If you're being treated for hypothyroidism while breastfeeding, you can safely continue to take your thyroid hormone replacement medication at your regular dosage without harm to your baby. Research shows the amount of thyroid hormone that comes through breast milk is less than 1 percent of the daily requirements a baby needs, so your medication has very little impact on your baby.

The question of taking antithyroid drugs for hyperthyroidism while breastfeeding is a bit more controversial, and you may want to explore the pros and cons further. The ATA says that since small amounts of propylthiouracil (PTU) and methimazole (MMI) can be found in breast milk, your doctor should put you on the lowest effective dose possible.

Experts recommend that the maximum daily dose of antithyroid medication while breastfeeding should be 20 mg of methimazole (MMI) or 450 mg of propylthiouracil (PTU).

A Word From Verywell

Once you've had postpartum thyroiditis, you have a substantially increased risk of developing it again in future pregnancies. When planning a pregnancy, or upon finding out you are pregnant, make sure to inform your doctors about any past thyroid issues. 

In addition, an episode of postpartum thyroiditis increases your risk of developing hypothyroidism or a goiter later on in life, so it's important to have your thyroid function evaluated annually.  

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