Postpartum thyroiditis: tiredness and anxiety after birth
Postpartum thyroiditis affects 5-10% of new parents and can mimic normal exhaustion. Learn its two phases, symptoms, and when to ask for a thyroid test.
In short
Postpartum thyroiditis is common. It affects roughly 5% to 10% of people after birth. It can cause fatigue, anxiety, or low mood that's easy to mistake for normal newborn exhaustion. It usually moves through two phases. First comes an overactive thyroid (racing heart, anxiety, feeling too hot). Then comes an underactive thyroid (low energy, feeling cold, low mood). A simple blood test can check for it. Ask your provider, especially if you've been diagnosed with postpartum depression. Thyroid function should be checked in that case too.
Sourced from StatPearls (NCBI Bookshelf), StatPearls (NCBI Bookshelf), citing ACOG/ATA/Endocrine Society guidance, Cleveland Clinic · Updated August 15, 2026
You're exhausted. Your anxiety feels bigger than normal new-baby nerves. Some days your heart races. Other days you can barely get off the couch. Everyone says it's just sleep deprivation, and maybe it is. But for many postpartum parents, something else is going on too. It's a temporary problem with your thyroid. The thyroid is the small gland at the base of your neck. Your thyroid quietly controls your energy, mood, and body temperature. It also controls metabolism (how your body turns food into energy).
People don't talk about postpartum thyroiditis as much as postpartum depression or anxiety. That's partly because its symptoms look a lot like normal new-parent exhaustion. But it's common. And a simple blood test can diagnose it. Knowing the pattern can help you tell the difference between "this is just the fourth trimester" and "my body needs help." This is about your thyroid, not your parenting or your feeding choices.
What is postpartum thyroiditis?
Postpartum thyroiditis happens when your immune system briefly attacks your thyroid gland, causing inflammation. It can start anytime within the first year after you give birth. It usually follows two phases, according to StatPearls (NCBI Bookshelf). First comes an overactive thyroid (called thyrotoxicosis). Then comes an underactive thyroid (called hypothyroidism).
It's also far from rare. StatPearls estimates it affects roughly 5% to 10% of people in the postpartum period. That's a lot of new parents whose fatigue, anxiety, or low mood has a real, treatable physical cause. It's not just the ordinary wear of caring for a newborn.
What happens in the first phase?
The first phase is an overactive thyroid. It typically starts 1 to 4 months after delivery, per StatPearls. Cleveland Clinic gives a slightly wider window, anywhere from one to six months postpartum. It notes this phase can last from as little as one week up to three months before it shifts.
During this phase, you might notice a racing heart (palpitations), anxiety, feeling too hot, or fatigue. Or you might notice nothing at all. StatPearls says this phase can be entirely symptom-free. That's part of what makes it so easy to miss. The anxiety and racing heart that show up in those early months can feel just like the general overwhelm of new parenthood.
What happens in the second phase?
The second phase is the opposite. It's an underactive thyroid that usually begins around 4 to 8 months postpartum, according to StatPearls. This phase brings low energy, feeling cold, weight gain, and depression.
The first phase can look like anxiety. This second phase can just as easily look like the low mood and exhaustion so many people expect to feel months into caring for an infant. That overlap is exactly why it's worth knowing this pattern exists. Then you have words for it if it happens to you.
Why does it get missed so often?
Postpartum thyroiditis symptoms overlap so closely with normal postpartum fatigue, mood swings, and weight changes. Because of this, the condition is often under-recognized and mistakenly attributed to other causes, per StatPearls. In other words, it's not that anyone is failing to notice you're struggling. It's that the symptoms genuinely look like what everyone expects postpartum life to feel like.
This is exactly why major medical groups have built a specific recommendation around it. The American Thyroid Association, the Endocrine Society, and the American College of Obstetricians and Gynecologists all recommend that thyroid function be evaluated in every postpartum person diagnosed with postpartum depression. This is cited by StatPearls. If you've received a postpartum depression diagnosis, a thyroid panel is a reasonable and recommended next question to raise with your provider. It doesn't replace mental health support. But it can identify a physical contributor that's treatable on its own track.
Can it affect breastfeeding?
Thyroid dysfunction after birth has also been linked with breastfeeding trouble. In one case-control study of 178 women cited by StatPearls, nearly twice as many participants with thyroid dysfunction reported lactation difficulties compared with those without it.
If you're finding breastfeeding harder than expected, that's not a reflection of effort or commitment. It can be one more thread connected to the same underlying hormonal shift. Whatever you decide about feeding, whether that's continuing to breastfeed, moving to formula, or combination feeding, that decision is yours. A thyroid issue is simply one more piece of information to bring to your provider, not a verdict on your parenting.
Will it go away?
The encouraging news is that postpartum thyroiditis is, for most people, temporary. Cleveland Clinic notes that it generally resolves within about 12 to 18 months of first noticing symptoms. At that point, the thyroid returns to normal function. Most people recover normal thyroid hormone production and no longer need medication.
That said, recovery isn't universal. Roughly 20% to 30% of people remain in the underactive (hypothyroid) phase, per Cleveland Clinic, and may need longer-term thyroid support. Either outcome is manageable once it's identified. A blood test can tell you what your thyroid is doing right now. That information can turn a vague, exhausting mystery into something with a name, a timeline, and a plan.
Frequently asked questions
How common is postpartum thyroiditis?
It's more common than most people realize. Postpartum thyroiditis affects roughly 5% to 10% of people in the postpartum period, according to StatPearls (NCBI Bookshelf). That means it's a routine possibility your care team should be thinking about, not a rare fluke.
Will postpartum thyroiditis go away on its own?
For most people, yes. Cleveland Clinic notes that postpartum thyroiditis generally resolves within about 12 to 18 months of first noticing symptoms. The thyroid then returns to normal function. Most people recover normal thyroid hormone production and no longer need medication. Though roughly 20% to 30% remain in the underactive (hypothyroid) phase and may need ongoing treatment.
Can postpartum thyroiditis affect breastfeeding?
It can be a contributing factor. In one case-control study of 178 women cited by StatPearls, nearly twice as many participants with thyroid dysfunction reported lactation difficulties compared with those without it. This isn't about anything you did. It's a physical hormonal shift that can make breastfeeding harder. It's worth mentioning to your provider if you're struggling.
I was diagnosed with postpartum depression — should my thyroid be checked?
Major medical organizations think so. The American Thyroid Association, the Endocrine Society, and the American College of Obstetricians and Gynecologists all recommend that thyroid function be evaluated in every postpartum person diagnosed with postpartum depression. This is noted by StatPearls. It's a simple blood test that can rule in or rule out a physical cause for what you're feeling.
What are the two phases of postpartum thyroiditis, and when do they happen?
Postpartum thyroiditis typically follows a two-phase course. The first, overactive phase usually starts one to four months after delivery (StatPearls). Cleveland Clinic puts the window at one to six months, lasting anywhere from a week to three months. The second, underactive phase usually begins around four to eight months postpartum. It can last well into the following year before resolving.
Sources
- Postpartum thyroiditis is a destructive autoimmune inflammation of the thyroid that can present anytime within the first year after delivery and typically follows a two-phase course of temporary overactive thyroid (thyrotoxicosis) followed by underactive thyroid (hypothyroidism). — StatPearls (NCBI Bookshelf)
- Postpartum thyroiditis affects roughly 5% to 10% of people in the postpartum period. — StatPearls (NCBI Bookshelf)
- The early, overactive-thyroid phase of postpartum thyroiditis typically occurs 1 to 4 months after delivery and can cause palpitations, anxiety, heat intolerance, or fatigue, or it can cause no symptoms at all. — StatPearls (NCBI Bookshelf)
- The later, underactive-thyroid phase of postpartum thyroiditis usually begins around 4 to 8 months postpartum and involves low energy, cold intolerance, weight gain, and depression. — StatPearls (NCBI Bookshelf)
- Because postpartum thyroiditis symptoms overlap so closely with normal postpartum fatigue, mood swings, and weight changes, the condition is often under-recognized and mistakenly attributed to other causes. — StatPearls (NCBI Bookshelf)
- Major medical groups — the American Thyroid Association, the Endocrine Society, and the American College of Obstetricians and Gynecologists — recommend that thyroid function be evaluated in every postpartum person diagnosed with postpartum depression. — StatPearls (NCBI Bookshelf), citing ACOG/ATA/Endocrine Society guidance
- Thyroid dysfunction after birth is linked with breastfeeding trouble: in one case-control study of 178 women, nearly twice as many with thyroid dysfunction reported lactation difficulties compared with those without it. — StatPearls (NCBI Bookshelf)
- The hyperthyroid (overactive) phase of postpartum thyroiditis usually begins one to six months after delivery and may last from one week up to three months. — Cleveland Clinic
- Postpartum thyroiditis generally resolves within about 12 to 18 months of first noticing symptoms, at which point the thyroid returns to normal function. — Cleveland Clinic
- Most people with postpartum thyroiditis recover normal thyroid hormone production and no longer need medication, but roughly 20% to 30% remain in the underactive (hypothyroid) phase. — Cleveland Clinic
Educational information, not medical advice — always consult your doctor.