Managing Thyroid In Pregnancy: Causes and Effects

The thyroid gland controls metabolism and produces two important hormones: thyroxine (T4) and triiodothyronine (T3). These hormones influence vital bodily functions, such as heart rate, energy levels, and growth. During pregnancy, an underactive or overactive thyroid gland may cause thyroid disorders.

These imbalances, if not controlled, may affect fertility, increase the risk of miscarriage, and raise the likelihood of complications such as caesarean deliveries and excessive bleeding after childbirth. This article covers the impact of thyroid health on the mother and baby's well-being and how thyroid disorders can be effectively managed during pregnancy.

What are the Physiological Changes in the Thyroid During Pregnancy?

Pregnancy induces significant changes in thyroid function owing to hormonal fluctuations, leading to several physiological adjustments in the female body. These include:

• Increased T4 and T3 Levels (Hormone Status)

The thyroid hormones T4 and T3 enhance the mother’s metabolic rate to ensure the baby’s proper development in the womb. The levels of these two hormones increase during pregnancy. 

• Decreased TSH levels (Thyroid-Stimulating Hormone)

The pituitary gland produces TSH, which prompts the thyroid to release T4 and T3. In pregnancy, however, due to the effect of the Human Chorionic Gonadotropin (hCG), a hormone produced by the placenta, the level of TSH decreases.

• Lower Levels of Iodine

Thyroid hormone production requires iodine. However, the renal clearance of iodine in the body increases during pregnancy. As a result, more iodine is excreted through urine, reducing its availability in the mother’s body.

• Increased Peripheral Iodothyronine Metabolism (Thyroid Hormone Breakdown)

The placenta produces deiodinases, specifically D2 and D3, which allow thyroid hormones to be activated and inactivated, respectively. The deiodinases convert T4 into T3 (the active form) or reverse triiodothyronine (the inactive form). These actions can modulate the functional dynamics of thyroid hormones during pregnancy.

• Enlargement of Thyroid Gland

Sometimes, the thyroid gland becomes enlarged in pregnant women due to the body's increased demand for thyroid hormones. If the thyroid gland is unable to meet this demand, the pituitary gland sends signals to stimulate the production of more hormones, which can lead to gland swelling.

Causes and Effects of Thyroid Disorders in Pregnancy

Mentioned below are the causes and effects of various thyroid disorders in pregnancy: 

Causes and Effects of Hypothyroidism in Pregnancy

Hypothyroidism occurs when the thyroid gland is unable to produce adequate hormones. Hashimoto's thyroiditis, an autoimmune disease that damages the thyroid gland, is a common cause of this condition in pregnancy.

Causes and Effects of Hyperthyroidism in Pregnancy

Hyperthyroidism is a condition in which the thyroid gland is overactive and produces too much hormone. Graves' disease, an autoimmune disease affecting the thyroid gland, is a common cause of hyperthyroidism in pregnancy. Also, high levels of human chorionic gonadotropin (hCG), commonly seen in severe morning sickness, can cause temporary hyperthyroidism during early pregnancy.  

Causes and Effects of Thyroid Nodules in Pregnancy

Thyroid nodules are lumps that can develop in the thyroid gland. They can consist of solid tissue or fluid. The risk of developing thyroid nodules is higher during pregnancy, and already existing nodules tend to enlarge.

Symptoms of Thyroid Disorders in Pregnancy

The symptoms that are commonly observed in cases of thyroid disorders in pregnancy are as follows:
Weight loss or insufficient weight gain during pregnancy

• Feeling nervous  
• Mood swings
• High blood pressure
• Tiredness
• Muscle weakness
• Shaky hands
• Sleeplessness 
• Irregular heartbeat
• Frequent bowel movements or diarrhoea
• Swelling in the front of the neck (Goiter)

Risk Factors of Thyroid Disorders in Pregnancy

Here are the common risk factors that can cause thyroid disorders in pregnancy:

• People with a family history of thyroid disease may increase the risk of thyroid dysfunction during pregnancy.
• Women suffering from Type 1 diabetes are also vulnerable to thyroid diseases during pregnancy.
• Those who have received high-dose neck radiation may experience thyroid complications during pregnancy.
• A BMI above 40 kg/m2 increases the risk of thyroid dysfunction in pregnant women.

Diagnosis of Thyroid Conditions in Pregnancy

For diagnosing thyroid disorders in pregnancy, the following tests are conducted:

Hyperthyroidism

The physician conducts tests to observe increased free thyroxine (FT4) and sometimes free triiodothyronine (FT3). Decreased levels of the Thyroid-Stimulating Hormone (TSH) are another marker for hyperthyroidism. In some instances, blood tests for thyroid antibodies are performed to determine if Graves' disease is the underlying cause of hyperthyroidism.

Hypothyroidism

In hypothyroidism, the physician looks for elevated levels of thyroid-stimulating hormone (TSH) and low levels of thyroxine (T4). Elevated TSH levels indicate that the thyroid gland has insufficient hormones, thereby responding to increased TSH produced by the pituitary gland.

Management and Treatment of Thyroid Disorders During Pregnancy

Thyroid disorders during pregnancy can be effectively managed through various treatments. Antithyroid drugs like propylthiouracil (PTU) in the first trimester and methimazole later help control hyperthyroidism, while beta-blockers alleviate symptoms like palpitations and sweating. 

Hypothyroidism is treated with levothyroxine to replace deficient thyroid hormones. In severe cases where medications are ineffective or cause side effects, surgery may be considered.

Risks and Complications Associated with Untreated Thyroid Disorders

Untreated hyperthyroidism during pregnancy can lead to severe complications for both mother and baby. These include conditions like preeclampsia, hypertension, and placental abruption, which pose significant risks to maternal health.

Babies may face issues such as premature birth, low birth weight, goitre, or congenital thyroid disorders. In rare cases, complications like heart failure or thyroid storm can become life-threatening without prompt treatment.

Impact of Thyroid Autoimmunity on Pregnancy

Thyroid autoimmunity, in terms of Hashimoto's thyroiditis and Graves' disease, is associated with an increased risk of complications such as miscarriage, premature birth, and fetal growth restriction.

Maternal thyroid antibodies may also affect fetal thyroid function and subsequently lead to developmental problems or congenital hypothyroidism. Thus, regular monitoring is required to avoid these complications.

Importance of Preconception and Prenatal Care

Preconception care is crucial for identifying thyroid disorders and managing them appropriately before pregnancy, thus improving health status during pregnancy and childbirth.

In addition, regular visits for prenatal care, with the additional support of thyroid function tests, enable adjustments to thyroid medicine to maintain the optimal functioning levels of hormones.

Lifestyle and Dietary Considerations

Doctors generally recommend pregnant women suffering from thyroid problems to follow these:

• Take thyroid medications such as levothyroxine at least 30 to 60 minutes before breakfast or about 3 to 4 hours after dinner.
• Take the medication on an empty stomach.
• Avoid taking thyroid medication within 4 hours of iron or calcium supplements.
• Wait for at least 30 minutes after taking the medication before consuming any food or beverages, including caffeinated drinks, as these may interfere with absorption rates.

In addition, a woman with thyroid disorder during pregnancy should include these foods in their diet plan:

• Approximately 250 micrograms of iodine per day
• Fruits such as berries, apples, bananas, grapes, citrus fruits, and pineapple, are rich in vitamins and antioxidants.
• Fish, eggs, meat, and poultry to support muscle development and boost energy levels.
• Whole grains, including oats, whole wheat bread, and barley.
• Dairy alternatives, such as cheese, coconut milk, cashew milk, coconut yoghurt, almond milk, and unsweetened yoghurt
• Herbal teas with cinnamon or ginger
• Almonds are high in fibre, protein, and minerals.

Conclusion

Thyroid disorders during pregnancy require careful attention due to their potential impact on both the mother and the developing baby. With timely diagnosis, proper monitoring, and effective treatment strategies, most complications can be avoided, ensuring a healthy pregnancy journey. Advances in medical research and understanding of thyroid health continue to improve outcomes, empowering expectant mothers and healthcare providers to make informed decisions. Prioritizing regular check-ups and open communication with your healthcare team is key to successfully managing thyroid conditions during pregnancy. Talk to your healthcare provider today to ensure your thyroid health is on track for a safe and healthy pregnancy.