- University of Cardiff researchers study effect of thyroid hormone replacement drug on pregnant women with mild hypothyroidism.
- If you are hypothyroid and pregnant don't forget to take your thyroid tablets. Thyroid tablets was found to lower the risk of still birth, early cesarean-section and low birth weight in the pregnant women.
- Study lead author declares early detection and intervention important.
About 2 to 3 % of pregnant women are diagnosed with hypothyroidism. This is a condition in which the hormone is secreted in lower quantities. The thyroid hormone is present in the base of the neck and the amount of thyroid hormone that is secreted plays a critical role in fetal development.
‘Thyroid hormone level important for pregnancy outcomes.’
Thyroid Hormone in Fetal DevelopmentPrevious studies have highlighted the significance of this hormone with fetal development. Researchers Pemberton HN and colleagues studied the effect of thyroid hormone levels and fetal brain development. They found that this hormone provided the signals that were required for the growth and maturation of the neuronal cells, the absence of which could lead to mental retardation in children.
The most important aspect of thyroid hormone levels on fetal brain development is the timing. The hormone should be present at the developmental stage to be beneficial. Studies have shown that the damages caused to the developing fetal cortex and hippocampus regions are permanent.
Thyroid Hormone Levels and Pregnancy ComplicationsThe thyroid hormone levels on fetal brain development have been extensively studied, however, the effect of mild hypothyroidism on pregnancy complications has not been fully researched. This study focuses on the effect of the thyroid hormone on pregnancy outcomes like stillbirth, early C-section and low birth weight.
Researchers from The University of Cardiff studied the effect of the hormone replacement drug levothyroxine on pregnancy outcomes.
The study utilized data from a survey as well as parameters that are usually collected in a clinical set up. These were combined to find a correlation. In the study, 13,000 women who were 12-16 weeks pregnant were analyzed, out of which 518 were found to have mild hypothyroidism. Out of the women with mild hypothyroidism, 263 did not receive any treatment for their condition.
The pregnancy outcomes that were studied include length of stay at the hospital, stillbirth rates, birth weight preterm delivery and the number of early caesarean sections.
The study found that women with mild hypothyroidism and who received levothyroxine had a lower risk for early caesarean deliveries and a lower risk for delivering a still born baby. Another interesting angle that was discovered in this study was that women with mild hypothyroidism who were undetected and did not receive treatment had a higher risk of delivering a still birth baby when compared with a woman with normal thyroid hormone function.
The study did not find any significant association between the level of thyroid hormone and other pregnancy outcomes. Dr. Peter Taylor who is the primary author of the study stated "Our work raises the possibility of providing real benefits from using a safe, cheap and well established treatment by simply extending it to the number of pregnant women we treat."
In addition to the benefit gained from this trial, Dr Taylor stressed that the earlier the detection of poor thyroid function and earlier the start of treatment with thyroid replacement drug, the better the outcomes for the mother as well as the child. "We should consider universal thyroid screening in pregnancy as it compares favourably in terms of cost-effectiveness with other conditions that we currently screen for," he further added.
Significance of Early TreatmentThere are two sources of thyroid hormone for the developing fetus, one from the mother and one from the fetus itself. However, the fetal hormone is available only after 12 weeks of gestation. There is substantial transfer of maternal hormone across the placenta, this is especially significant during the early stages of development when the fetus hasn't begun secreting its own. Early treatment of mild hypothyroidism will aid in better health of the fetus as well as in pregnancy outcomes.
Types of Hypothyroidism that Affect Fetal Development
1. Maternal Hypothyroidism: Severe hypothyroidism usually leads to infertility and is not usually associated with pregnancy. When it does occur, it leads to death of the fetus in the womb or even gestational hypertension. Hypothyroidism that is mild is an alarming factor in pregnancy as it is usually subclinical and detected too late. In some cases it is caused due to an autoimmune disorder where antibodies attack the thyroid hormone or could pass the placenta and affect the fetal thyroid gland.
2. Fetal Hypothyroidism: This is a rare congenital condition that leads to poor development of the fetal thyroid hormone, which leads to poor thyroid hormone levels. The condition does not affect the growth of the fetus as the hormone is provided by the mother via the placenta. However, it is important to detect this condition soon after birth as it could lead to a permanent mental retardation called cretinism.
3. Iodine Deficiency: Low level of iodine in the mother leads to hypothyroidism in the mother as well as the fetus. Iodine deficiency is the most significant preventable cause of mental retardation in children.
Mild hypothyroidism is a silent condition in pregnant women that can lead to complication in the fetus as well as in pregnancy outcomes. It is important to identify this condition and to take hormone replacement drug to aid the mother and child.
- Thyroid Hormones: Pregnancy and Fetal Development - (http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/thyroid/thyroid_preg.html)
- Transplacental thyroxine and fetal brain development - (https:www.ncbi.nlm.nih.gov/pmc/articles/PMC152596/)
- Thyroid hormones and fetal brain development - (https:www.ncbi.nlm.nih.gov/pubmed/16170282)