Thyroid disorders affect an estimated 350 million people worldwide^1,2 and are especially common in women.³ Sadly, when undiagnosed, thyroid disorders can impact fertility,^4,5 fetal development and the health of the mother and baby.⁶

To mark this year’s International Thyroid Awareness Week (May 25-31), an annual campaign developed by Merck in close collaboration with Thyroid Federation International and this year with ThyroidChange, we talked to Prof. Dr. med. Frank-Raue from Heidelberg about the importance of mothers and babies maintaining good thyroid health and how this can be achieved.

Each year millions of women dream of having a baby yet are faced with fertility challenges. These challenges occur for many reasons, including untreated thyroid disorders. Prof. Dr. med. Frank-Raue, please can you explain the role of the thyroid gland in thyroid hormone production and why maintaining good thyroid health is important for fertility?

The thyroid is a butterfly shaped gland in the front of the neck, it produces thyroid hormones that are essential for metabolism of the body and regulating many bodily functions.^7,8

Thyroid hormones are integral in fertility and are important factors in oocyte development and implantation. Undiagnosed thyroid dysfunction can make it difficult to conceive. An underactive (hypothyroidism) and an overactive (hyperthyroidism) thyroid function are associated with menstrual irregularities and increased rates of infertility. However, once these disorders are diagnosed and managed, there is no reason why a successful pregnancy and a healthy baby should not be possible.⁹

We understand thyroid health is important for fertility, but can you explain why good thyroid health should be maintained throughout pregnancy?

Thyroid hormones are essential for the growth of the fetus/baby and critically important for fetal brain development. Normal thyroid hormone levels are especially important in the first months of pregnancy as the fetus depends on maternal thyroid hormone supply via the placenta.¹⁰

Women with poorly managed hypothyroidism have an increased risk of pregnancy complications and impaired fetal outcome. On the maternal side the risk of miscarriage and hypertension during pregnancy is increased. The fetus/baby has an increased risk of fetal loss, slower fetal development, low birth weight, premature birth, and lower IQ.¹⁰

A pregnant woman who has poorly controlled hyperthyroidism has an increased risk of pregnancy induced hypertension, maternal heart failure and a severe thyroid hyperfunction called a thyroid storm. While, the fetus/baby has an increased risk of fetal loss, growth restriction within the uterus, low birth weight, premature delivery, and neurobehavioral disorders in later life.¹¹

Iodine deficiencies for mother and baby is the theme for this year’s ITAW. Why is it important for mothers and babies to maintain the correct levels of iodine?

Iodine is essential for thyroid hormone production and it can be obtained only by foods that contain it like iodized table salt, fish or other marine products, or iodine supplements. During normal pregnancy, the thyroid gland is stimulated by pregnancy hormones and increases thyroid hormone production by nearly 50%, which implies a 50% increase in daily iodine requirements. This adaption process starts very early in pregnancy. In some countries there is iodine deficiency of various severity. Therefore, The World Health Organization recommends 250ug daily intake of iodine for pregnant and lactating women. If maternal iodine supply is sufficient the fetus will also be well supplied via the placenta⁹.

Now you have explained the importance of mothers maintaining good thyroid health, can you advise women planning to be pregnant or already pregnant how this is achieved?

The guidelines recommend that all women trying to get pregnant or newly pregnant should have a clinical evaluation. A thyroid hormone measurement is recommended if certain risk factors exist, such as a history of thyroid dysfunction, clinical signs or symptoms of thyroid dysfunction, autoimmune disorders, history of pregnancy losses or infertility.^9,12

In addition, it is recommended that women should take a daily oral supplement that contains 150ug iodine, optimally started 3 months in advance of planned pregnancy.^9,13

For women with hypothyroidism who are trying to conceive, their thyroxine substitute dosage should be optimal before conception and should be increased in early pregnancy, depending on the capacity of the remaining thyroid tissue to increase the production rate of thyroid hormones. Usually, an increase of 30 to 50% is necessary.^9,14

Women who are affected by hyperthyroidism (Graves’ disease), should consult their physicians before conception about the following points: 1. Postponing pregnancy until a stable thyroid gland function is established; 2. Risks and benefits of all treatment options; 3. Fetal monitoring if Grave’s antibodies are markedly elevated in maternal blood testing