Can Hypothyroidism Cause Infertility?

Updated on September 18th, 2020
Hypothyroidism and infertility

If we’ve been diagnosed with an underactive thyroid or hypothyroidism — or may wonder if it may lead to problems during pregnancy or even a miscarriage. Hypothyroidism is linked to miscarriages, so it’s essential to recognize the signs of this condition. 

Understanding the Thyroid’s Role

The thyroid gland is above your collarbone (in your neck) that produces hormones involved with many of our body’s activities. It plays a crucial function in our body’s hormonal and metabolic balance.1 When something’s wrong with our thyroid, there’s a good chance the rest of our body and its processes — like pregnancy — will be adversely impacted.

What Is Hypothyroidism?

Thyroid hormone controls our body’s metabolic processes. When we have hypothyroidism, the thyroid does not produce adequate thyroid hormone to keep these processes going at their optimal rate, and they start slackening down. This can impact various aspects of our health, including whether we have a healthy pregnancy.

An Underactive Thyroid During Pregnancy

Our thyroid must normally be functioning during our pregnancy, both for developing our baby’s health and our health. Multiple complications can occur in pregnant women with hypothyroidism:

  • Anemia 
  • Preeclampsia
  • Stillbirth
  • Low birth weight
  • Miscarriage 
  • Rarely, congestive heart failure can occur

What causes maternal hypothyroidism?

A common reason for underactive thyroid in pregnant women is Hashimoto’s thyroiditis or Hashimoto’s disease [1]. This autoimmune disease attacks when your immune system forms immune proteins (antibodies) that attack the thyroid.

This, in turn, causes the gland to produce too little thyroid hormone. People with this condition may have symptoms of hypothyroidism, or they may have no effects.

Other reasons for hypothyroidism include iodine deficiency, before treatment for hyperthyroidism (when the thyroid makes excess thyroid hormone), and surgery to eliminate thyroid tumors.

The thyroid may also become underactive after childbirth. About seven percent of women get inflammation of the thyroid (postpartum thyroiditis) in the initial year after giving birth. This problem begins with hyperthyroidism, which most often clears up without treatment in a few months or weeks.

But sometimes, the inflammation leads to hypothyroidism. In most instances, hypothyroidism clears up on its own. In nations where there is not sufficient iodine in their diet, iodine deficiency is a major cause of hypothyroidism. The thyroid gland needs iodine to develop thyroid hormones.

In the United States, iodine is not lacking in the diet due to iodized salt. However, breastfeeding or pregnant women need more iodine than normal and should increase their crucial mineral intake.

[Also Read: Natural Treatments for Hypothyroidism]

Miscarriage Risk and Hypothyroidism — What the Research Shows

Studies indicate that having an underactive thyroid may be associated with some kinds of pregnancy loss.

Research has found that SCH (subclinical hypothyroidism) could mean an increased risk of preterm delivery and placental abruption, both of which may occur in later pregnancy loss. 

The evidence is less convincing about a link between first-trimester miscarriage and hypothyroidism. Some studies suggest that TAI (thyroid autoimmunity) may be associated with first-trimester miscarriage, but other trials contradict the relation, and the matter is still up for investigation. 

A 2014 Chinese study found that women with both thyroid autoimmunity and subclinical hypothyroidism have a greater risk of miscarriage between weeks four and eight of their pregnancies.  

Recognizing the Symptoms of Hypothyroidism

According to the U.S. NLM (National Library of Medicine), symptoms of hypothyroidism include:

  • Weight gain
  • Fatigue
  • Cold intolerance
  • A puffy face
  • Constipation
  • Joint and muscle pain
  • Dry, thinning hair 
  • Dry skin
  • Irregular or heavy menstrual periods and fertility problems
  • Decreased sweating
  • Depression
  • Slowed heart rate 

If you are bothered that you may have hypothyroidism, ask your physician about screening. She or he can make a diagnosis based on your symptoms and a straightforward blood test.

Thyroid Hormone During Pregnancy

Suppose you are not suffering from an underactive thyroid. In that case, you will be administered with levothyroxine (a synthetic thyroid hormone). Synthetic levothyroxine is identical to our natural thyroid hormone and is safe for your baby (developing) [2].

If you were already using levothyroxine before you got pregnant, your physician would probably increase your dose during pregnancy to maintain your optimal thyroid function. It’s best to talk to your physician about your dosage before you are pregnant. 

Your thyroid function must be checked every four weeks until mid-pregnancy and then at least once close to 30 weeks.

[Also Read: Connection Between Fertility & Thyroid]

How does hypothyroidism affect the fetus?

During the initial few months of pregnancy, the fetus depends on the mother for thyroid hormones. Thyroid hormones are critical in the growth and normal brain development of the fetus. Hypothyroidism in the mother may have long-lasting effects on the fetus. 

How is thyroid function tested?

You should have a blood test that measures thyroid hormone (T4 or thyroxine) and serum thyroid-stimulating hormone (TSH) levels to check for hypothyroidism. Hypothyroidism is often suspected when T4 levels are below normal, and TSH levels are above normal.

Who should undergo thyroid function screening?

Routine screening for hypothyroidism while pregnant is not suggested. A pregnant woman with a history of hypothyroidism, hypothyroidism symptoms, or other endocrine system conditions must be screened.

How is hypothyroidism treated during pregnancy?

Thyroid hormone replacement is made use to treat the mother. The dose of thyroid hormone replacement therapy is based on the individual’s thyroid hormone levels. Thyroid hormone levels may fluctuate during pregnancy. And, the thyroid replacement dosage can also change. 

Bottom Line

Thyroid hormone levels must be checked every four weeks during the first half of pregnancy. The treatment is essential and safe for both fetus and mother. Routine screening for all newborns includes a thyroid hormone level test.

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