Pregnancy and Hypothyroidism

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Originally published on 26th June 2016
Last updated on 29th May 2019

I’m going to cover how hypothyroidism can develop during or after pregnancy, what to do if you’re a thyroid patient who falls pregnant, your mental health and pregnancy and postpartum thyroiditis.

How can hypothyroidism develop during/after pregnancy?

As pregnancy is stressful on the body, it can induce hypothyroidism. For some women, this starts during pregnancy, but it’s after pregnancy that a lot are diagnosed. Some recover after a month or two, but many are left with hypothyroidism for the rest of their lives, requiring medication.

During pregnancy, the body goes through many hormonal changes and the immune system makes adjustments in order to preserve the fetus and not reject it as a foreign invader.

The Th-1 suppression ends after birth and this causes the immune system to surge. If it is already unstable, then this can trigger the start of Hashimoto’s Thyroiditis. Hashimoto’s is usually triggered.

Hashimoto Thyroiditis is an autoimmune disease where the immune system attacks healthy thyroid gland tissue, slowly destroying it. This causes hypothyroidism. Hypothyroidism in pregnancy is usually caused by Hashimoto’s and occurs in three to five out of every 1,000 pregnancies.

The thyroid gland usually enlarges with pregnancy, but not to a noticeable amount.

Additionally, if you have the autoimmune version of hypothyroidism called Hashimotos, you’ll want to keep a check on adequately treating your hypothyroidism and antibodies, since some experts state that thyroid antibodies cross the human placenta and could attack your baby’s thyroid.

What if I know I’m hypothyroid already but am now pregnant?

As soon as you know you are pregnant, tell your doctor and get a full thyroid panel booked in as soon as possible. That’s a FULL thyroid panel. Not just TSH and Free T4. Free T3 and thyroid antibodies too. Make it your mission to look after yourself and your baby as well as possible.

In the first part of pregnancy, the fetus relies completely on the mother to provide the thyroid hormones for its development. For someone with a perfectly health thyroid gland and function, their body is able to meet that extra demand easily. In a woman with hypothyroidism, her body may not be able to. According to the Endocrine Society’s 2007 Clinical Guidelines for the Management of Thyroid Dysfunction during Pregnancy and Postpartum, thyroid medication usually needs to be increased in dosage, by 4-6 week gestation and may well require a 30-50% increase in dosage.

Most women require an increase in thyroid medication when pregnant, to support the developing baby. Failure to properly maintain adequate thyroid levels whilst pregnant can result in complications such as miscarriage, pre-eclampsia, anaemia, stillbirth and the baby developing congenital hypothyroidism itself. So it’s very important to be tested regularly, often every 6-12 weeks, throughout your pregnancy. Adjustments to your medication should then be made accordingly.

If you’re ‘subclinical’ or ‘borderline’ hypothyroid, your doctor may wish to start you on thyroid medication or increase it so that you’re well within range to reduce risk of miscarriage. The risk of miscarriage is higher in women with subclinical hypothyroidism, compared to women with normal thyroid function (euthyroidism)[1].

TSH During Pregnancy

The ATA recommends the use of the following ranges during pregnancy:

  • First trimester: 0.1-2.5
  • Second trimester: 0.2-3.0
  • Third trimester: 0.3-3.0

Blogger and thyroid advocate Hypothyroid Mom started her site in memory of the baby she lost due to her thyroid levels not being maintained correctly, and fights to stop this from happening to other women and babies. So maintaining optimal thyroid levels are important.

Some researchers believe that one factor in the development of autism is severe hypothyroidism in their mothers.

Mental Health and Pregnancy

Although controversial, I’m going to say it: postnatal depression could actually be due to low thyroid function.

So if you have been told you have postnatal depression, it is definitely worth having a full thyroid panel done to check your thyroid. In fact I feel that thyroid screening should become mandatory during all pregnancies. Whether you’re diagnosed with a thyroid condition or not, I believe that thyroid levels should be monitored. As explained above, some women develop thyroid problems during pregnancy.

I say it’s controversial to claim that some of the postnatal depression cases out there could be due to poor thyroid function, because some would suggest I am implying that postnatal depression isn’t a real thing in its own right. But it is, I acknowledge that. What I’m saying is that the thyroid could be responsible for at least some of these cases, because of its link to mental health. You can’t argue that this can’t be true, when low thyroid function is proven to be linked to poor mental health. There will be women out there who have been diagnosed with postnatal depression, have hypothyroidism, and have no idea. Only testing a full thyroid panel, definitely checking the all important Free T3, will rule this out.

Some people will know they’re hypo, be on medication for it, but be under-medicated (with Free T4 and Free T3 levels not being optimal) and be diagnosed with depression because of this.

If someone has postnatal depression after pregnancy, then there is a chance they may have developed Hashimoto’s and/or hypothyroidism, which is causing the symptoms.

The link is thought to involve T3, one of the hormones a healthy thyroid should be producing. T3 is the most active thyroid hormone and required for a lot of things.

T3 has an important role in the health and optimal functioning of your brain, including: your cognitive function, ability to concentrate, mood, memory and attention span and emotions and ability to cope with life’s stresses. T3 interacts with brain receptors and makes the brain more sensitive to chemicals such as Serotonin and Norepinephrine, which affects your alertness, memory, mood and emotion.

So if your doctor failed to check your thyroid levels with the correct thyroid tests (TSH, Free T3 and Free T4), when you showed signs of poor mental health, then you may have mental health issues caused by an inadequately treated thyroid problem, most likely a low T3. So postnatal depression could actually be caused by thyroid levels being out of whack.

If you have had your thyroid levels checked and been told they’re fine, make sure they are in fact optimal. It can make a lot of difference.

Postpartum Thyroiditis

Postpartum Thyroiditis is where the thyroid gland becomes inflamed after pregnancy, and this happens to about 5-7% of women, usually within a few months of giving birth. Interestingly, this is also a form of autoimmune disease.

This usually presents as a painless, small enlargement of the thyroid, and can cause either hyperthyroid or hypothyroid symptoms.

This can also lead to postpartum depression because of its impact on thyroid function.

Common Symptoms

Similar to subacute thyroiditis, there are potentially two phases to postpartum thyroiditis. The inflammation and release of thyroid hormones in to the blood usually first causes symptoms of hyperthyroidism:

  • Anxiety
  • Increased sensitivity to heat
  • Insomnia
  • Irritability
  • Rapid heartbeat or palpitations
  • Tremor
  • Unexplained weight loss

These usually occur within a few months of giving birth. It is important to figure out if it’s postpartum thyroiditis or Graves’ disease with proper testing. 

As thyroid cells are continually attacked,  signs and symptoms of hypothyroidism can develop:

  • Lack of energy/fatigue/weakness
  • Increased sensitivity to cold/cold hands and feet
  • Constipation
  • Dry skin
  • Difficulty concentrating/brain fog/confusion
  • Aches and pains
  • Depression

Most women who experience postpartum thyroiditis return to normal thyroid function after about a year, however, around a third develop permanent hypothyroidism.


There are women in the Facebook support group that I run, who have been misdiagnosed with postnatal depression, when they actually had hypothyroidism, and taking thyroid medication has helped this or even cleared it up completely. This is scary and shocking, and for this reason, I feel that thyroid screening should become mandatory during all pregnancies.

Whether you’re diagnosed with a thyroid condition or not.

Like Dr Barry Durrant-Peatfield, I feel anyone diagnosed with depression or anxiety should be screened for thyroid problems, too. And using a full thyroid panel, not just TSH.

You can click on the hyperlinks in the above post to learn more and see references to information given.

Book on thyroid disease and pregnancy: Your Healthy Pregnancy with Thyroid Disease: A Guide to Fertility, Pregnancy, and Postpartum Wellness

References:

[1] Haixia Liu, Zhongyan Shan, Chenyan Li, Jinyuan Mao, Xiaochen Xie, Weiwei Wang, Chenling Fan, Hong Wang, Hongmei Zhang, Cheng Han, Xinyi Wang, Xin Liu, Yuxin Fan, Suqing Bao, and Weiping Teng, November 2014, Maternal Subclinical Hypothyroidism, Thyroid Autoimmunity, and the Risk of Miscarriage: A Prospective Cohort Study, https://www.liebertpub.com/doi/10.1089/thy.2014.0029

If you found this article beneficial, please take a moment to share it so we can help others get better with hypothyroidism and Hashimoto's, whilst also raising awareness. "Be Your Own Thyroid Advocate."

Written by Rachel, The Invisible Hypothyroidism

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