What Is Postpartum Thyroiditis?
Postpartum thyroiditis is inflammation of the thyroid gland in the first year after giving birth, in women whose thyroid worked normally before pregnancy. It is an autoimmune condition. During pregnancy the immune system is partly held back; after the birth it rebounds, and in some women it attacks the thyroid.
It matters on a mental health site for one reason: its symptoms look almost exactly like postpartum depression, anxiety and ordinary newborn exhaustion, so it is easy to miss. The National Institutes of Health warns that the symptoms can be mistaken for the baby blues.
It is painless, it is diagnosed with a blood test, and it is treatable, including while breastfeeding.
How Common Is It?
About 1 in 20 women develop postpartum thyroiditis in the year after giving birth, according to the NIH and the American Thyroid Association’s 2017 guideline. Individual studies have found anywhere from 1.1% to 16.7%, largely because they defined and tested for it differently, and the American Thyroid Association’s patient guidance puts the U.S. figure at 5% to 10%.
Some women are at much higher risk:
| Group | Risk of postpartum thyroiditis |
| Thyroid antibodies (TPO or thyroglobulin antibodies) positive in the first trimester | 33% to 50%, rising with higher antibody levels |
| Type 1 diabetes | 3 to 4 times the usual rate |
| A previous episode of postpartum thyroiditis | High; estimates range from about 20% to 70% per later pregnancy |
| Other autoimmune conditions, such as lupus, or a history of Graves’ disease | Raised in small studies |
| Family history of thyroid disease | Listed as a risk factor |
Having thyroid antibodies does not mean you will get it. Many antibody-positive women never develop thyroid problems. It can also occur after a miscarriage or abortion, although how often is not known.
The Two Phases
Inflammation first lets stored thyroid hormone leak out of the gland, which can make the thyroid overactive for a while. As the hormone stores run down and the gland is damaged, it can then become underactive.
| Overactive (hyperthyroid) phase | Underactive (hypothyroid) phase | |
| When | Usually 2 to 6 months after birth, sometimes up to a year | Usually 3 to 12 months after birth |
| How long | Up to about 3 months, and always resolves on its own | Often months; most recover within a year or so |
| How it feels | Often mild or unnoticed | More often noticeable |
| Symptoms | Anxiety, irritability, trouble sleeping, racing heart, feeling hot, weight loss, fatigue | Exhaustion, low mood, poor memory and concentration, feeling cold, dry skin, weight gain, constipation, aches |
Not everyone goes through both. According to the American Thyroid Association’s guideline, about half of women have only the underactive phase, about a quarter have only the overactive phase, and about a quarter have both, one after the other. The underactive phase is the one most often diagnosed, partly because the overactive phase is easy to miss.
Why It Gets Mistaken for Postpartum Depression
Read the symptom lists again with a new baby in mind. Anxiety, irritability and poor sleep in the overactive phase. Exhaustion, low mood and foggy thinking in the underactive phase. Almost every one of those is also a symptom of postpartum depression, postpartum anxiety or simply caring for a newborn.
The American Thyroid Association notes that the overactive phase is often overlooked because its symptoms get put down to the stress of having a new baby. Timing makes it harder still: symptoms usually are not present at the six-week postpartum visit, and a normal thyroid test at six weeks does not rule it out.
Does Postpartum Thyroiditis Cause Depression?
This is where the evidence is less clear than many websites suggest.
- There is an association. Two meta-analyses found that women with thyroid antibodies had about 1.5 times the risk of perinatal or postpartum depression. An earlier study found depression in 47% of antibody-positive women compared with 32% of antibody-negative women, whether or not their thyroid levels were abnormal.
- But it is inconsistent. A large study of pregnant women in the Netherlands found no significant link between thyroid antibodies or thyroid hormone levels and postpartum depression, and the American Thyroid Association describes the research as inconsistent.
- And treating the thyroid did not prevent depression. In a trial, giving thyroid hormone to antibody-positive women after birth made no difference to rates of postpartum depression.
The honest summary: postpartum thyroiditis is not proven to cause postpartum depression. What is certain is that an underactive thyroid produces symptoms that look like depression, and that is a reason to check. The American Thyroid Association strongly recommends that everyone with depression, including postpartum depression, be screened for thyroid problems.
How It Is Diagnosed
Postpartum thyroiditis is diagnosed with blood tests:
- TSH (thyroid-stimulating hormone) and free T4 show whether the thyroid is overactive or underactive.
- TPO antibodies are raised in most women with postpartum thyroiditis, which supports the diagnosis.
If the thyroid is overactive, the next question is whether it is postpartum thyroiditis or Graves’ disease, a different condition that also appears after pregnancy and needs different treatment. Clues include:
- Timing. An overactive thyroid within the first three months after birth is much more likely to be thyroiditis; after about six months, Graves’ disease becomes more likely.
- TSH receptor antibodies (TRAb). These are positive in almost all cases of Graves’ disease and usually negative in postpartum thyroiditis.
Radioactive thyroid scans are rarely needed. If you are breastfeeding, radioactive iodine-131 must not be used; other scan types can be used if breast milk is pumped and discarded for several days.
Treatment
The Overactive Phase
- Often no treatment is needed. This phase always resolves on its own.
- For bothersome symptoms like a racing heart or anxiety, a beta-blocker such as propranolol or metoprolol, at the lowest dose that helps, is the treatment of choice, usually for a few weeks.
- Antithyroid drugs (such as methimazole) do not work and are not recommended. The gland is leaking stored hormone, not overproducing it.
- Follow-up matters. TSH should be rechecked about four to eight weeks after the overactive phase, or sooner if new symptoms appear, to catch the underactive phase.
The Underactive Phase
- Levothyroxine, a thyroid hormone pill, is used for women with symptoms, and also for women who are breastfeeding or trying to get pregnant.
- Women not started on treatment should have TSH checked every four to eight weeks until thyroid function returns to normal.
- After about 12 months, doctors can try stopping levothyroxine, but not while you are trying to conceive or pregnant.
Breastfeeding
Both main treatments are compatible with breastfeeding. According to the NIH’s LactMed database, the amount of propranolol a breastfed baby receives is small and not expected to cause harm, and levothyroxine is a normal component of breast milk with no adverse effects reported in infants at replacement doses. An untreated underactive thyroid can also affect milk supply.
Will It Go Away?
Usually, but not always, and not necessarily for good.
- Most women’s thyroid function returns to normal within about a year to a year and a half.
- A substantial minority develop permanent hypothyroidism. The American Thyroid Association guideline gives 10% to 20% overall, and studies that followed women for longer found that 10% to 50% of those who initially recovered developed it later.
- The risk keeps rising over years, which is why the American Thyroid Association strongly recommends a TSH test every year for anyone who has had postpartum thyroiditis.
Can It Happen Again?
Yes. Estimates of the chance of it returning in a later pregnancy vary widely, from about 20% on the American Thyroid Association’s patient page to 70% in its clinical guideline, which is based on a small study. Either way the risk is real. If you have had it before, get your thyroid checked before trying for another baby, because an underactive thyroid in early pregnancy needs prompt treatment.
Taking levothyroxine, iodine or selenium during pregnancy to prevent postpartum thyroiditis does not work and is not recommended.
When to Ask for a Thyroid Test
Ask your ob-gyn, midwife or primary care doctor to check your thyroid if, in the first year after birth, you have:
- Symptoms of depression or anxiety, or a diagnosis of postpartum depression
- A racing heart, shakiness, heat intolerance or unexplained weight loss
- Exhaustion that feels out of proportion to your sleep, feeling cold, or unexplained weight gain
- Difficulty with milk supply
- Type 1 diabetes, known thyroid antibodies, or a previous episode of postpartum thyroiditis
A thyroid test does not replace care for depression, and a thyroid problem does not rule out depression. Both can be present, and both are treatable. If you are struggling with your mood, the PHQ-9 takes a few minutes and scores itself on this site, and you can find a therapist who treats postpartum depression.
If you are having thoughts of harming yourself, call or text 988, or call or text the National Maternal Mental Health Hotline at 1-833-TLC-MAMA (1-833-852-6262).
Frequently Asked Questions
What is postpartum thyroiditis?
It is inflammation of the thyroid in the first year after giving birth, caused by the immune system rebounding after pregnancy. It can make the thyroid temporarily overactive, underactive, or one after the other.
How common is postpartum thyroiditis?
About 1 in 20 women get it in the year after giving birth. The risk is much higher, 33% to 50%, in women with thyroid antibodies in early pregnancy, and 3 to 4 times higher in women with type 1 diabetes.
Is postpartum thyroiditis reversible?
Usually. Most women’s thyroid function returns to normal within about a year. But a substantial minority develop permanent hypothyroidism, sometimes years later, so a yearly TSH test is recommended.
What are the symptoms of postpartum thyroiditis?
In the overactive phase: anxiety, irritability, trouble sleeping, a racing heart and weight loss, though many women notice little. In the underactive phase: exhaustion, low mood, poor concentration, feeling cold, dry skin and weight gain.
Can postpartum thyroiditis cause depression or anxiety?
It can cause symptoms that look like depression and anxiety. Whether it directly causes postpartum depression is not proven; studies conflict, and treating the thyroid did not prevent depression in a trial. Anyone with postpartum depression should have their thyroid checked.
How is postpartum thyroiditis treated?
The overactive phase often needs no treatment, or a beta-blocker such as propranolol for symptoms. Antithyroid drugs do not help. The underactive phase is treated with levothyroxine when there are symptoms or when a woman is breastfeeding or trying to conceive.
Can I breastfeed with postpartum thyroiditis?
Yes. Propranolol and levothyroxine are both considered compatible with breastfeeding.
Would a thyroid test at my six-week checkup have caught it?
Not necessarily. Symptoms usually start after the six-week visit, and a normal result at six weeks does not rule it out. If symptoms appear later, ask for a repeat test.
