T3 and T4 during Pregnancy


It is estimated that 1 out of 5 women have one form of thyroid dysfunction or another. This statistic is especially true during pregnancy. As a matter of fact, women with no prior thyroid related health issues before becoming pregnant may be more susceptible to either an overactive or underperforming thyroid gland during and even after pregnancy.

Indeed pregnancy greatly influences the way the thyroid gland generates  the T3 and T4 hormones. Hyperthyroidism is a condition caused by an overactive thyroid gland, where the level of T3 and T4 hormones generated is on the high side. On the other hand, hypothyroidism is the opposite, where the thyroid gland does not generate sufficient levels of thyroid hormones.

Hyperthyroidism Shuts down TSH production

In a situation where the thyroid gland of a pregnant woman is generating too much T3 and T4, the Thyroid stimulating hormone or TSH which encourages the thyroid gland to generate T3 and T4 hormones literally shuts down.

Hyperthyroidism will significantly raise the level of metabolism and this condition may affect pregnant women aged between 20 and 40 years. If a pregnant woman has hyperthyroidism, they usually experience symptoms that may go undetected because of their similarity to the normal symptoms associated with pregnancy.

Some of these symptoms include: anxiety, tiredness, and an overwhelming feeling of warmth. However, maternal hyperthyroidism can be dangerous as it could lead to the following health issues:

  • high blood pressure and hypertension,
  • a high propensity of miscarriage,
  • increased risk of premature birth, and a high likelihood that the baby would be born with a birth weight that is alarmingly low.



Graves’ Disease a Common Cause of Hyperthyroidism in Pregnant Women

Graves’ Disease causes the immune system to be more active than normal and in the process produces antibodies or immune proteins that adversely affects the thyroid gland. The thyroid gland becomes bigger than usual and produces significantly more thyroid hormone than usual. Graves’ Disease causes hyperthyroidism in pregnant women and this is why testing and treatment is very important even before a woman gets pregnant.


Transient Gestational Thyrotoxicosis

Transient Gestational Thyrotoxicosis is a temporary form of hyperthyroidism that may cause pregnant women to experience very severe vomiting and nausea. This firm of hyperthyroidism may be caused by the high levels of human chorionic gonadotropin or hCG which is a hormone released during pregnancy. However, Transient Gestational Thyrotoxicosis is a condition that usually resolves itself between the 14th and 18th week of pregnancy and therefore may not require any antithyroid medication to resolve the condition.

It is also important to note that hyperthyroidism or the exceeding production of T3 and T4 thyroid hormones may occur due to the presence of many tiny lumps in the thyroid gland know as nodules. The nodules are responsible for generating exceeding amounts of T3 and T4 thyroid hormones.

Some Symptoms of very High T3 and T4 Hormones in Pregnant Women

When the level of T3 and T4 hormones in a pregnant woman is higher than normal, she is likely to experience some of the following symptoms:

  • A rapid heart rate,
  • A feeling of being too warm or hot especially when the weather is not uncomfortable,
  • Hand tremors,
  • Tiredness,
  • Insomnia,
  • Increased anxiety, and
  • weight loss despite observing good eating habits.