TSH Levels During Pregnancy

High TSH Levels During Pregnancy: Causes, Complications, And Management

TSH levels during pregnancy vary according to different trimesters. Managing TSH levels during pregnancy is important as abnormal levels may lead to various pregnancy complications.

Complications include miscarriage, low birth weight, preterm labor, and anemia. It may also affect the overall health of the mother and fetus. There are various causes of high and low TSH levels. Regular screening of TSH levels in pregnant women is required, especially in women already on thyroid medications. Medicines during pregnancy should be taken strictly as prescribed to avoid potential interactions with thyroid medications.

What Are Normal TSH Levels?

The normal level of Thyroid Stimulating Hormone (TSH) is required for proper functioning. If the level of TSH is high, it indicates that the thyroid gland is not making enough thyroxine hormone. This condition is termed as hypothyroidism. A low level of TSH indicates that the thyroid gland is making too much thyroxine hormone. This condition is termed as hyperthyroidism. To test for the TSH levels, the TSH profile is tested which includes testing T3, T4, and TSH levels. The test is also known as thyrotropin test. The test is performed by taking a small sample of blood.

The normal level of Thyroid Stimulating Hormone in healthy adults is 0.4 mIU/L to 4.0 mIU/L. If the patient has elevated levels of TSH on repeated tests, the person may have hypothyroidism. The value of TSH may change during pregnancy. TSH levels may vary according to the trimester. The normal value of TSH in the first trimester ranges from 0.6 mIU/L to 3.4 mIU/L while it is 0.37 mIU/L to 3.6 mIU/L in the second trimester. The third trimester has the normal TSH range of 0.38 mIU/L to 4.04 mIU/L.

What Are The Causes Of High TSH Levels?

There are various causes of high TSH levels;

Iodine Deficiency

Iodine is important for the synthesis of thyroxine hormone. The deficiency of iodine may lead to a low level of thyroxine leading to an increased level of TSH.

Hashimoto’s Disease

It is an autoimmune disease. In this disease, the body produces antibodies that damage various tissues of the body including the thyroid gland. The exact reason for this is not known.


Various medications such as lithium may lead to hypothyroidism.

Elevated Response To Hyperthyroidism Management

Sometimes the treatment done to manage hyperthyroidism may become over-responsive leading to hypothyroidism.

What Are The Causes Of Low Tsh Levels?

A low level of Thyroid Stimulating Hormone generally indicates hyperthyroidism. This means that the thyroid gland is secreting an abnormal amount of thyroxine hormone. Hyperthyroidism may lead to an increased rate of metabolism. It may cause irregular heartbeat and unintentional weight loss. Following are the causes of low TSH levels:


Hyperthyroidism may lead to low TSH levels. The cause of hyperthyroidism may be permanent or temporary. This may be due to autoimmune diseases or pregnancy-related thyroiditis.

The Central Cause Of Hypothyroidism

TSH is secreted by the pituitary gland when stimulated by Thyroxine releasing hormone secreted by the hypothalamus. Thus, there might be a problem in the hypothalamus or pituitary gland that may lead to a low level of TSH.

Over Response Of Thyroid Medications

Overresponse to medications administered to increase the level of thyroxine may lead to low levels of TSH.

What Are The Complications Due To High TSH Levels During Pregnancy?

Abnormal TSH levels may lead to various complications during pregnancy including miscarriage. Thus, maintaining a normal TSH level is vital for the health of the mother and fetus. Following complications may develop in the presence of high TSH levels:

Hypotony And Hypotonic Contractions

These may be due to reduced calcium, muscular tissue changes and other reasons.


APGAR is low in pregnancy until the due term.

Abnormal Fetal Cardiac Rhythm

Tachycardia or bradycardia may occur in the fetus due to maternal hypothyroidism.

Other Complications

Other complications due to hypothyroidism in pregnancy include miscarriage, anemia, premature birth, stillbirth, and low birth weight.

What Are The Tips To Maintain Normal Tsh Levels During Pregnancy?

Following measures help maintain normal levels of TSH during pregnancy;


As pregnancy may lead to abnormal TSH levels, the women, while planning to get pregnant, should undergo a comprehensive evaluation of the thyroid profile. Special care should be taken by women who have a family history of thyroid disease.

Healthy Diet

Maintaining a healthy diet during pregnancy may reduce the effect of hypothyroid symptoms.

Regular Monitoring

Regular monitoring of TSH levels during pregnancy is important.

Avoid Interactions

Various drugs and supplements are administered during pregnancy. Take medications strictly as scheduled by your doctor to avoid interactions.

Increase Dose

If you are on thyroid supplementation, inform your doctor as soon as you are pregnant. Your doctor may increase the dose of your thyroid medication to manage an increased level of TSH due to pregnancy.

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