Screening for thyroid health is not a part of the routine medical examination women in the United Kingdom (UK) receive during pregnancy or treatment for infertility but a recent study makes a strong case for including it in the nation’s universal screening protocols. Jason Waugh, editor-in-chief of the British medical journal, The Obstetrician & Gynaecologist (TOG), said, “Thyroid the most common endocrine condition affecting women of reproductive age.”

Amanda Jefferys led the study of thyroid health and female reproduction from the Southmead Hospital’s Bristol Centre for Reproductive Medicine in Bristol, England. One goal of her study is to highlight the importance of thyroid function on female reproduction. Another is to use this knowledge to improve reproductive outcomes.

Thyroid Function

The thyroid, one of the largest endocrine glands in the human body, sits just below the Adam’s apple in the neck. It secretes hormones that govern metabolism: how efficiently the body uses energy, how effectively it makes proteins, and how the body responds to other hormones. These functions are critical to healthy growth and development, especially development of the brain. Any deviation from a woman’s healthy thyroid function before, during, and after conception can produce a tremendous impact on her reproductive health.

Thyroid Disease

Thyroid disease falls into two types:

  • Hyperthyroidism (overactive thyroid)
  • Hypothyroidism (underactive thyroid)

There are many causes for either type of thyroid disease.


An overactive thyroid can contribute to menstrual irregularities that make reproduction difficult. The Jefferys study found that 1.5% of all women in the general population suffer from hyperthyroidism. The percentage is much greater —  2.3% — in women seeking treatment for fertility problems.


Approximately 0.5% of all women of reproductive age experience underactive thyroid function. When hypothyroidism occurs during childhood or adolescence, sexual maturity can be delayed. In adulthood, it contributes to menstrual problems sometimes severe enough to make ovulation impossible.

Thyroid Function and Pregnancy

At this time in the UK, women who seek treatment because they have difficulty conceiving are not routinely screened for thyroid health although the link between thyroid disease and infertility has been known for quite some time.

When conception succeeds, miscarriage becomes a risk if thyroid disease is present. In the general population, approximately one in five pregnancies (20%) ends in miscarriage. One percent of couples of reproductive age experience recurrent miscarriage (three consecutive miscarriages). Healthy embryonic development is closely associated with the mother’s healthy thyroid function; many miscarriages happen because of impaired development of the embryo that is sometimes linked to thyroid dysfunction. Jefferys finds the risk of miscarriage in women with poor thyroid function another reason to add screening to the universal screening requirements.

Thyroid disease, especially hyperthyroidism, can affect the pregnancy at any stage. Women with thyroid disease are at increased risk for preeclampsia, fetal growth restriction, preterm delivery, heart failure, and stillbirth.

Jefferys concludes that “with appropriate screening and prompt management, these risks can be significantly reduced.”


  1. "TOG release: New review looks at the effect of thyroid disorders on reproductive health." Royal College of Obstetricians & Gynaecologists. Royal College of Obstetricians & Gynaecologists, 22 Jan. 2015. Web. 9 Mar. 2015.
  2. Jefferys, Amanda, Mark Vanderpump, and Ephia Yasmin. "Thyroid dysfunction and reproductive health." Wiley Online Library. John Wiley & Sons, Inc., 23 Jan. 2015. Web. 9 Mar. 2015.