Thyroid in Reproduction

Clarisa R. Gracia, MD, MSCE

The thyroid is a vital endocrine organ that regulates many physiologic functions in the human body. In particular, the thyroid plays a critical role in reproduction. Thyroid hormones modulate hypothalamic–pituitary–gonadal function in both females and males. For example, in females, aberrations in thyroid function may influence fertility by interfering with normal ovarian follicle development and ovulation. Even subtle abnormalities in thyroid function have been associated with impaired fertility and increased risks of miscarriage. During pregnancy, maternal thyroid requirements increase, and normal thyroid function is very important for a healthy pregnancy, from both a maternal and fetal standpoint. Higher risks of pregnancy complications such as placental abruption, preeclampsia, gestational diabetes, and preterm delivery have been associated with thyroid conditions. Because maternal thyroid hormones are critical for infant growth and development, infants born to mothers with thyroid abnormalities have an increased risk of neonatal respiratory distress, NICU admissions, and even death. Moreover, infant neurocognitive abnormalities have been linked to maternal thyroid disease, as a major function of maternal and fetal thyroid hormone includes brain development.

Thyroid conditions such as hyperthyroidism, hypothyroidism, and thyroid nodules are common during the reproductive years. Patients with these conditions require special consideration, as thyroid diseases and their treatments can have a substantial impact on fertility, pregnancy, and the health of offspring. While controversial, treatment of individuals with subtle thyroid abnormalities, such as subclinical hypothyroidism and thyroid autoimmunity, may also be considered, as these conditions have been linked to adverse reproductive and neonatal outcomes as well.

The goal of this series entitled The Thyroid and Reproduction is to explore the impact of common thyroid conditions on fertility, reproductive outcomes, pregnancy, and neonatal health. A major emphasis has also been placed on reviewing screening recommendations, diagnostic strategies, and the management of a variety of thyroid conditions in reproductive-age individuals who plan to conceive or who are pregnant. The following articles have been included.

Management of hyperthyroidism during the preconception phase, pregnancy, and the postpartum period examines the impact of hyperthyroidism on the neonate and methods for diagnosis and management of this condition around the time of conception, pregnancy, and postpartum. Important information regarding the potential risks and benefits of treatment options on maternal, fetal, and neonatal health are discussed in detail.

Overview of hypothyroidism in pregnancy describes the common etiologies of hypothyroidism and known pregnancy and neonatal complications related to maternal hypothyroidism during pregnancy. Moreover, this article provides clinically relevant guidance on treatment and management of hypothyroidism during pregnancy.

The diagnosis and management of subclinical hypothyroidism to improve reproductive and neonatal outcomes has been an area of substantial debate. Two articles in this series provide a comprehensive overview of this topic.

• The impact and management of subclinical hypothyroidism for improving reproductive outcomes such as fertility and miscarriage

• Subclinical hypothyroidism: impact on fertility, obstetric, and neonatal outcomes

Thyroid autoimmunity and reproductive function reviews the literature supporting an association between thyroid autoimmunity and poor reproductive outcomes, including miscarriage and preterm birth. Data regarding strategies for the screening and management of thyroid autoimmunity to improve reproductive outcomes are outlined as well.

Thyroid cancer in pregnancy provides guidance on methods to evaluate and manage thyroid nodules and cancer during pregnancy. Treatment differs from the nonpregnant female, as clinicians must weigh the risks and benefits of each treatment option for the mother and fetus.

Finally, Thyroid dysfunction and male reproductive physiology explores the impact of thyroid function on male reproduction. This review describes thyroid physiology in the male and focus on presenting the evidence supporting an association between thyroid dysfunction and measures of male fertility and sexual health.