Thyroid and fertility

The Link Between the Thyroid and Fertility

The thyroid gland is an organ located at the bottom front of your neck shaped like a butterfly which produces important hormones. The thyroid’s main function is to control metabolism, but it has a big impact on the menstrual cycle and fertility too. The pituitary gland in the brain produces thyroid stimulating hormone (TSH), which signals the thyroid to release T3 and T4. When there’s an imbalance of the thyroid hormones, it can make it more difficult to conceive and carry a pregnancy to term. To learn all about the connection between the thyroid and fertility, keep reading our factsheet.

What are the types of thyroid disorders?

Thyroid disorders are a group of conditions which cause the thyroid gland to overproduce (hyperthyroidism) or underproduce (hypothyroidism) thyroid hormones T3 and T4. Thyroid autoimmunity is the most common autoimmune disorder in women in their reproductive years and increases the risk of developing a thyroid disorder.

Women are much more likely to have thyroid problems than men – 5 to 8 times more in fact. 2-4% of women in the reproductive age group have hypothyroidism while around 1-2% have hyperthyroidism. Both hyperthyroidism and hypothyroidism have a negative impact on fertility.

How do thyroid disorders impact fertility?

The thyroid hormones are very important for conception and pregnancy. They are vital for the body to produce estradiol and progesterone. So, having abnormal TSH levels can reduce fertility by interfering with ovulation and the luteal phase of the menstrual cycle. That means that either there’s no egg waiting to be fertilized by sperm or it’s more difficult for a fertilized egg to implant in the womb.

If the egg does implant, there’s a greater risk for miscarriage. According to a 2020 study, up to 25% of women who experience recurrent miscarriages have a thyroid disorder.

Hypothyroidism is associated with hyperprolactinemia, which reduces fertility as well. Around 46% of infertile patients with hypothyroidism have hyperprolactinemia. Having thyroid antibodies can harm egg quality too.

Beyond that, an uncontrolled thyroid disorder can cause complications during pregnancy, including premature birth, poor growth of the baby, and high blood pressure.

Thyroid disorders can affect male fertility too by damaging overall sperm quality, count, motility (movement), and morphology (movement). This can make it harder for sperm to fertilize an egg.

In total, about one-third of subfertile patients have a thyroid disorder, making it a major cause of fertility problems.

Symptoms of a thyroid problem

Hyperthyroidism (overactive thyroid) can cause the following symptoms:

  • Light, irregular and missed periods (amenorrhea)
  • Weight loss
  • Irregular heartbeat
  • Nervousness and irritability
  • Trembling hands
  • Heat sensitivity
  • Sleeping problems
  • Sweating
  • Thin hair and skin
  • Weak muscles
  • Enlarged thyroid


Hypothyroidism (underactive thyroid) has the following physical signs:

  • Heavy and frequent periods
  • Fatigue
  • Sore or cramped muscles
  • Poor memory
  • Dry skin and hair
  • Weight gain
  • Cold sensitivity
  • Loss of sex drive
  • Constipation


If you suspect you have a thyroid problem and have had difficulty getting pregnant or carrying a pregnancy to term, we can help you out. When you test your fertility with LEVY Health, we look at all possible causes and personalize your blood test to fit your symptoms. Our advanced thyroid diagnostics panel goes beyond checking your TSH levels (like some at-home fertility tests do) – we do a comprehensive evaluation of thyroid biomarkers, including TSH, T3, and more to determine 6 potential diagnoses. If you are diagnosed with a thyroid disorder, we will make a custom treatment plan to get your fertility back on track.

Treatment for thyroid disorders to improve fertility

Thankfully, thyroid problems are easily manageable through treatment with medication. Once the thyroid hormones are back in balance, fertility should return and you should be able to have a healthy pregnancy. Medication also improves male fertility problems caused by an overactive or underactive thyroid.

A 2012 study of 394 infertile women found that about 24% of them had hypothyroidism. After treatment, over 76% were able to conceive within one year.

Besides medication, ensuring you have enough vitamin D can help keep your thyroid healthy and may lower the amounts of thyroid antibodies. Vitamin D is also a critical nutrient for fertility.

Once you get pregnant, be sure to tell your OBGYN about your thyroid condition. Your medication dosage will likely need to be adjusted and you’ll need to be more closely monitored throughout your pregnancy to protect your and your baby’s health.

Takeaway about thyroid and fertility

Thyroid disorders are a major cause of fertility problems and miscarriage because they can interfere with the menstrual cycle and make it more difficult for an embryo to successfully implant in the uterus. Hypothyroidism and hyperthyroidism can also cause complications during pregnancy. You can find out if you have a thyroid problem with a blood test, and getting your hormones back in balance with medication can help your fertility return to normal.


Pregnancy and fertility in thyroid disorders. British Thyroid Foundation. Accessed 01 July 2022.

Hypothyroidism and infertility: Any connection? Mayo Clinic. Accessed 01 July 2022.

Verma I et al.: Prevalence of hypothyroidism in infertile women and evaluation of response of treatment for hypothyroidism on infertility. Int J Appl Basic Med Res. 2012;2(1):17-19.

Unuane D, MD, PhD & Velkeniers B, MD, PhD: Impact of thyroid disease on fertility and assisted conception. Best Practice & Research Clinical Endocrinology & Metabolism. 2020;34(4):101378.

Monteleone et al.: Female infertility related to thyroid autoimmunity: the ovarian follicle hypothesis. Am J Reprod Immunol. 2012;66:108-114.

The Connection Between Thyroid Disorders and Fertility. EndocrineWeb. Accessed 01 July 2022.

Gude D: Thyroid and its indispensability in fertility. J Hum Reprod Sci. 2011;4(1):59-60. 

General Information/Press Room. American Thyroid Association. Accessed 06 July 2022.

Hyperthyroidism (overactive thyroid). Mayo Clinic. Accessed 06 July 2022.

Underactive thyroid (hypothyroidism) Symptoms. NHS. Accessed 06 July 2022.

Rugge JB et al: Screening for and Treatment of Thyroid Dysfunction: An Evidence Review for the U.S. Preventive Services Task Force. Agency for Healthcare Research and Quality (US). 2014. Rockville (MD).

Shrestha S et al.: Association of Thyroid Profile and Prolactin Level in Patient with Secondary Amenorrhea. Malays J Med Sci. 2016;23(5): 51-56.

Hyperthyroidism and Graves’ Disease. University of Michigan Health. Accesseed 02 September 2022.


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