How Can Hypothyroidism Affect Pregnancy

Pregnancy and Hormones

Pregnancy comes with various hormonal and physiological changes. An increase in estrogen and progesterone levels are associated with pregnancy as they are the major pregnancy hormones. The level of hormones changes drastically e.g. a woman produces more estrogen in a single pregnancy then a woman will produce throughout her life without being pregnant. Apart from these, levels and functions of various other hormones changes during pregnancy as well.

Thyroid Hormones and Pregnancy

Hypothyroidism and Pregnancy

Introduction to Thyroid Gland

The thyroid gland is a two inches long gland located in front side of the neck just below the cricoid cartilage (the Adam’s apple) and is found wrapped around trachea. It is butterfly shaped gland weighing 0.52 ounces (15 grams). The two lobes of the gland are similar to butterfly wings attached to each other with a middle part known as isthmus.

Function of Thyroid gland

Thyroid gland plays an important role in the production and storage of body’s thyroid hormones. To produce these hormones, the gland requires a signal from specific areas of the brain that are pituitary gland and hypothalamus. After receiving the signal, brain releases a thyroid stimulating hormone (TSH) which eventually results in the production of thyroid hormones by the gland. An adequate amount of iodine either from food as a mineral or from iodized salt is necessary for maintain a constant level of these hormones.

Thyroid Hormones and Pregnancy

The major hormones produced by thyroid gland are triiodothyronine (T3) and thyroxine (T4). These hormones are involved in metabolism (a process that transforms food into energy), maintaining blood pressure, body temperature, muscle strength, cholesterol level and even the heart rate.  Another hormone produced by thyroid gland is calcitonin which play a vital role in calcium metabolism. All these hormones are regulated by the release of thyroid-stimulating hormone (TSH) produced by the pituitary gland in brain.

During pregnancy, the level of thyroid hormone varies as it is concerned with the growth and development of baby’s brain and nervous system.  In the first three months (first trimester) of pregnancy baby depends on the mother for thyroid hormones and it is exchanged through mother’s placenta. After almost 12 weeks, fetus develops its own thyroid gland. That’s the time when it starts producing the thyroid hormones but still depends on mother’s until around 18 weeks.

It is necessary to ensure the presence of adequate amount of iodine in the pregnant females because thyroid hormones production depends on it. Thus, an appropriate level of iodine could be achieved through the intake of prenatal vitamin with enough iodine. This will ensure that the baby gets required amount of iodine from the mother.

Pregnancy and Thyroid Disease

The imbalance in thyroid hormones can result in the complications for human body. Sometimes any abnormality associated with thyroid gland could cause the increase or decrease from the normal level of these hormones.   Too much production occurs when the gland becomes overactive and this condition is known as hyperthyroidism. This condition result in speeding up of the metabolism. Contrary to this, when the thyroid gland becomes underactive and the body functioning slows down, the state is called as hypothyroidism.

Human chorionic gonadotropin (HCG) and estrogen are two hormones related to pregnancy that can result in the increase in thyroid levels. Thus, making it difficult to diagnose the thyroid disease in pregnant women. Yet your healthcare professional will be able to diagnose the complication through the symptoms. Even though it is necessary to get yourself regularly checked for the thyroid problems, it is equally important to get it checked if you are pregnant or are planning to get pregnant.

Moreover, it is important to know that through regular thyroid function tests and proper medication one can protect the baby’s healthy and can have a healthy pregnancy.

Hypothyroidism and Pregnancy

Women of child-bearing age are prone to thyroid disease thus it is common to have thyroid disease associated complication during pregnancy. These complications can equally affect the mother and baby.

Etiology of Hypothyroidism

One of the major etiologic factors of hypothyroidism is Hashimoto’s thyroiditis. It is an autoimmune disorder in which body’s own immune system produces antibodies and attacks the thyroid gland. This could result in the enlargement of thyroid gland, called as goiter. Lack of adequate amount of iodine in your diet can also cause hypothyroidism and goiter both. Treatment of hyperthyroidism that includes radioactive iodine therapy or thyroid surgery may also results in hypothyroidism. But in most cases the specific cause of hypothyroidism still remains unknown.

Clinical Features of Hypothyroidism

Hypothyroidism occurs when the production of thyroid hormones is reduced by the thyroid gland. As a result, slowing down the metabolism and causing various symptoms. In the beginning, the clinical features of hypothyroidism are not noticeable and remains asymptomatic. Symptoms develop with time and can end up into more severe ones. Slowing down of the metabolism means body will lack energy and some of the common hypothyroidism associated symptoms are weight gain, fatigue, muscular cramps, weakness, joint pain, slow heart rate and shortness of breath with activity etc. symptoms can also includes hoarse voice, constipation, brittle hair, dry itchy skin, hair loss, brittle nails, loss of sex drive etc. In severe conditions, it might lead to clinical features including difficulty in concentration and learning in the baby born to hypothyroid mother, irregular menstrual cycle, infertility and might results in miscarriage as well.

Effects of Hypothyroidism on the Pregnant Mother

Females who have an undiagnosed hypothyroidism before they get pregnant may contributes in severe complications later. However, during pregnancy if a female develops hypothyroidism the symptoms are only mild and, in some cases, its asymptomatic. Pregnancy and hypothyroidism come with some common features thus it is important to get yourself checked for hypothyroidism. As even a mild but untreated hypothyroidism can develop complications for the mother and fetus both. Hypothyroidism associated pregnancy complications includes miscarriage, anemia, premature birth, abruptio placentae, preeclampsia (a sudden rise in blood pressure in the third trimester of pregnancy) and postpartum hemorrhage. In rare cases, it might result in congestive heart failure.

The reason for irregular periods associated with hypothyroidism is that it prevents ovulation i.e. the release of the egg from the ovary. Usually after a monthly cycle, an egg is released from the ovary, but in those who develops hypothyroidism the frequency of egg release reduces as a result effecting the normal menstrual cycle. Moreover, the increase risk of miscarriage is because hypothyroidism interferes with embryo development.

Effects of Hypothyroidism on the Fetus

Thyroid hormones are vital for the development of baby’s nervous system. If a mother suffering from hypothyroidism remains undiagnosed on untreated, especially during the first trimester, it can adversely affect the baby’s brain. This is because during the first 3 months, fetus solely depends on mother for its thyroid hormones. Thus, hypothyroidism could interfere with normal development and can cause low IQ problems as well as impaired psychomotor (mental and motor) development in the baby. Also, if you have untreated hypothyroidism during pregnancy, there are chances for you to have premature baby with weigh less than normal and have lowered brain development.

Researched says that babies born to mother with thyroid diseases are at increased risk of brain, heart and kidney defects. As thyroid hormones are crucial for baby’s development and can affect their intellectual development, they also increase the risk of physical abnormalities like extra finger, ear deformities or cleft palate.

Hypothyroidism and Breastfeeding

Thyroid hormones are involved in the normal breast development. Hypothyroidism causes lack of the production of thyroid hormones as a result affecting breast development and eventually milk production. Treated mothers show no issues in the milk supply but those with untreated condition struggle with the adequate supply of milk. Furthermore, it is totally safe for a breastfeeding mother to continue with thyroid medication.

It is common to know that hypothyroidism might affect pregnancy and production of milk. But some females may develop thyroid disease after giving birth to the child. Indeed, breastfeeding helps the baby to nourish and grow yet it can affect the level of thyroid hormones in mother. As a result, aiding in thyroid problems. Breastfeeding mother can develop an increase production of thyroid hormones which can lead to a condition called postpartum thyroiditis. It is good to know that over a certain period of time this condition goes away on its own and in case of prolonged duration doctor can prescribe a low does medicine.

In contrary to this, there is enough evidence available that supports the prevention of thyroid problems associated with breastfeeding. It says that breastfeeding can help prevent thyroid problems in both the mother and the baby. One can prevent autoimmune thyroid disease as well as thyroid cancer through regular breastfeeding.

Diagnosis of Hypothyroidism

For the diagnosis of hypothyroidism, main test that is recommended by the doctors is measuring blood levels of TSH. Higher level of TSH in blood depicts that the pituitary gland has responded and made more TSH, but it is remained unused to produce sufficient thyroid hormone. Other blood tests include measuring the T4 levels, which is a hormone directly produced by the thyroid gland. Low level of T4 in blood would indicate hypothyroidism.

Some of the reasons that tends to make a woman at higher risk of developing thyroid diseases are a family history of thyroid disease, type 1 diabetes mellitus, thyroid autoimmunity or it can be any other autoimmune condition. Thus, for diagnosis, it is important to tell the doctor every detail about your history. It would be an ideal condition if every woman when gets pregnant or is planning to get pregnant should be tested for the presence of a thyroid disease. Otherwise prenatal counselling can be carried out after conceiving. Doctor recommends the females who are a higher risk for developing thyroid disease to get the TSH level checked or carry out thyroxine blood tests or any other thyroid blood tests in order to have a healthy pregnancy.

Frequent Monitoring of the Thyroid Levels

Incorrect dose can adversely affect the health as well, so regular monitoring is important. For example, in case of higher dose of thyroid replacement hormone, women may end up in developing a treatment-induced hyperthyroidism. That means the metabolism of your body suddenly increased the required level. As a result, treatment-induced hyperthyroidism can cause osteoporosis (bone loss and bone thinning), nervousness and heart palpitations.

Even if the dose of your hypothyroidism is adjusted, it is necessary to have blood levels checked regularly. Because hypothyroidism is a progressive disease with can stay there for your whole life. So, regardless of whether you are pregnant of not, it is better not to leave it ignored. The dose adjustment can vary over the period of time.


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