What happens to your thyroid and Hashimoto’s after pregnancy

by Emma Bakh and Dr. Vedrana Högqvist Tabor

Photo: Pxhere. Design: BOOST Thyroid.

Photo: Pxhere. Design: BOOST Thyroid.

Pregnancy has a major impact on the thyroid and on the immune system. After the pregnancy is over, your body will take time to re-adjust to the change in the progesterone - estrogen balance, as well as to the new, mostly lower requirements for thyroid hormones. This means that you should take an extra care with your health during the months following pregnancy.

What happens to your thyroid after pregnancy?

During pregnancy, your thyroid produces more hormones than usual. While some or all of the hormones may come from the thyroid replacement T4 or natural thyroid, the thyroid can also go into overdrive trying to produce enough hormones. It may get enlarged, which can be felt as a swelling in the neck or goiter, and having trouble swallowing foods (1).

What happens to your immune system after pregnancy?

During pregnancy, the hormone progesterone increases, which prevents inflammation and autoimmune flare-ups. After pregnancy, progesterone levels drop sharply and rapidly, causing a re-activation of the immune system which leads to triggering inflammations and flare-ups. This happens because the other sex hormone, estrogen, becomes more abundant (2).

The increased need for extra T3 and T4 happens rapidly in the first part of pregnancy, up until 10 or 12 weeks, and then stays at that level or grows a bit (3, 4).

Even if you don’t have any detectable problems with your thyroid, you might develop thyroid problems. In the majority of cases this is because you may actually have a latent thyroid disease, meaning the disease was never so severe that it needed attention. The most common thyroid condition occurring after pregnancy is called postpartum thyroiditis (PPT) (5).

What is postpartum thyroiditis?

Postpartum thyroiditis (PPT) can affect up to 2 in 10 women after pregnancy (6–8).

By medical definition, PPT is the occurence of a thyroid problem (excluding Grave’s disease) in the first year after pregnancy in women who had normal thyroid function before pregnancy (9, 7, 10).

How does postpartum thyroiditis develop?

Postpartum thyroiditis is caused by the autoimmune condition Hashimoto’s, and pregnancy just speeds up the development. Normally it can take up to 10 years from when the first antibodies are detected to the development of an underactive thyroid (8,10–12). But pregnancy shortens this period, as hormones progesterone and estrogen drastically change the immune system.

When will PPT develop?

In people who didn’t have any noticeable thyroid problems before pregnancy, PPT may happen within the first year, most noticeably at 2–6 months after pregnancy. The course of the disease can take two main forms:

Classic form: experienced by 1 in 4 of people, a phase where the thyroid becomes overactive, an overactive thyroid phase, followed by a decline in thyroid function and an underactive thyroid, and then a recovery phase where the thyroid starts producing enough hormones.

Straight underactive thyroid: experienced by 4 in 10 people (10,13). The thyroid of 1 in 2 of people experiencing PPT will eventually become permanently underactive (10).

Repeated pregnancies will increase the risk of developing PPT and an underactive thyroid (4,8), and timely testing of hormone levels before, during and after pregnancy will help understand and adjust for your body’s needs.

What are the symptoms of PPT?

  • Tiredness

  • Impaired memory

  • Depression

  • Increased sensitivity to cold

  • Dry skin

How is PPT treated?

Postpartum thyroiditis is considered an underactive thyroid disorder and treated with the same medications. The synthetic T4 hormone replacement levothyroxine is prescribed to people breastfeeding or wishing to become pregnant (7,13). Thyroid-boosting supplements such as selenium and Omega-3 fatty acids are also highly recommended (10,14–16).

Your doctor will help you to find the best way to manage your thyroid and immune health after pregnancy. Track your symptoms in the BOOST Thyroid app to facilitate this conversation with your doctor.


  1. Carney LA, et al. Thyroid Disease in Pregnancy, 2014

  2. Alvergne A et al. Is Female Health Cyclical? Evolutionary Perspectives on Menstruation, 2018

  3. Glinoer D. et al. Regulation of maternal thyroid during pregnancy, 1990

  4. Ain KB. et al. Reduced clearance rate of thyroxine-binding globulin (TBG) with increased sialylation: A mechanism for estrogen-induced elevation of serum TBG concentration, 1987

  5. Stagnaro-Green A. Postpartum Management of Women Begun on Levothyroxine during Pregnancy, 2015

  6. Muller AF, et al. Postpartum thyroiditis and autoimmune thyroiditis in women of childbearing age: recent insights and consequences for antenatal and postnatal care, 2001

  7. Di Bari F, et al. Autoimmune Abnormalities of Postpartum Thyroid Diseases. Front Endocrinol, 2017

  8. Inaba H, et al. Postpartum Thyroiditis, 2018

  9. Andersen SL, et al. Hypothyroidism incidence in and around pregnancy: a Danish nationwide study, 2016

  10. Stagnaro-Green A. Approach to the Patient with Postpartum Thyroiditis, 2012

  11. Carlé A, et al. Epidemiology of subtypes of hypothyroidism in Denmark, 2006

  12. Strieder TGA, et al. Prediction of Progression to Overt Hypothyroidism or Hyperthyroidism in Female Relatives of Patients With Autoimmune Thyroid Disease Using the Thyroid Events Amsterdam (THEA) Score, 2008

  13. Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and Postpartum, 2011

  14. Wu Q, et al. Low Population Selenium Status Is Associated With Increased Prevalence of Thyroid Disease, 2015

  15. Duntas LH, et al. Selenium: an element for life, 2015

  16. Breese McCoy SJ. Coincidence of remission of postpartum Graves’ disease and use of omega-3 fatty acid supplements, 2011