Trouble Getting Pregnant? It Might Be Your Thyroid

It’s a little gland in your neck shaped like a butterfly, but the thyroid is powerful. It regulates everything from body temperature to metabolism, but most of us never think about our thyroid until something goes wrong. In some cases, it can be an underactive gland that manifests as hypothyroidism and symptoms like hair loss or weight gain; for others, it’s an overactive gland leading to hyperthyroidism and a rapid heartbeat or insomnia. And for a growing number of people, papillary thyroid cancer is the issue.

But some women have no idea their thyroid isn’t working properly until they’re having trouble trying to conceive. Fortunately, with the right kind of diagnosis and thyroid treatment, it’s still possible for them to become mothers.

Experts have long believed that thyroid issues can affect fertility. A review published in The Obstetrician & Gynaecologist found that 2.3 percent of women with fertility problems had hyperthyroidism compared to 1.5 percent of those in the general population. The researchers also found that 0.5 percent of women of reproductive age have hypothyroidism. Some women with hypothyroidism are symptomatic, experiencing everything from fatigue and weight gain to hair loss and menstrual abnormalities, but many have no symptoms and are only diagnosed after a routine blood test. The researchers found that both clinically apparent (showing signs and symptoms) and subclinical (undetectable) hypothyroidism are associated with infertility.

Most women with hypothyroidism and hyperthyroidism have evidence of autoimmunity, which means their body makes antibodies that attack their own thyroid glands. Thyroid autoantibodies can, however, also be detected in many women with normal thyroid function, and it’s not clear whether these women are at an increased risk of infertility.

The thyroid gland is central to growth and development, and it plays an important role in reproduction. Thyroid disease has been linked to increased risk of problems during pregnancy, including miscarriage, preeclampsia, poor fetal growth, and premature birth, and thyroid hormone is essential for brain and skeletal development in the fetus. In cases of hyperthyroidism, the thyroid gland fails to produce certain hormones, which can interfere with ovulation. In women with hypothyroidism, autoimmune or pituitary disorders may be at the root of fertility trouble.

The American College of Obstetrics and Gynecology recommends routine thyroid screening for women starting at age 35. The process is simple and involves regular blood tests to monitor hormone levels. The study’s authors believe testing should also be done for women with fertility problems and repeated early pregnancy loss.

If hypo- or hyperthyroidism is responsible for a woman’s infertility, proper treatment will restore her ability to conceive. “Evaluating thyroid function is only small part of a comprehensive infertility workup,” says One Medical’s Malcolm Thaler, MD, “but testing is easy and correcting the problem is rarely difficult.” The treatment for hypothyroidism is one daily pill before breakfast to replace the missing hormones. Hyperthyroidism treatment can involve medications to inhibit the synthesis of thyroid hormones, radioactive iodine to destroy thyroid tissue, and surgery for overactive thyroid nodules. Treatment in both cases is generally safe during pregnancy, and close monitoring of hormone levels during pregnancy helps promote normal fetal development and reduces the risk of miscarriage.