Pregnancy: the ‘ultimate stress test’ for the thyroid gland
Pregnancy is a time when a mother’s thyroid gland needs to increase its hormone production by at least 50%! This is for her pregnant body’s needs for thyroid hormones, and to supply her baby with thyroid hormones.
Up until 16-20 weeks, the baby relies completely on the mother’s thyroid hormones. This is until their thyroid gland matures and produces thyroid hormones. This maturity is not reached until the 3rd trimester.
Thyroid hormones cross the placenta to the baby for critical brain development. If a mother has mild or moderate thyroid gland dysfunction during pregnancy, this can result in neurodevelopmental problems in the baby.
THIS is why comprehensive thyroid testing is essential; ideally in the preconception phase, and/or during each trimester of pregnancy.
A healthy - and nutritionally supported - thyroid gland can meet the increased thyroid hormone requirements of pregnancy. But there is no way of knowing its functioning unless the right blood tests are done.
However, when the thyroid gland is not functioning 100%, thyroid pathology can often be triggered (or worsened) by the metabolic demands of pregnancy.
If a mother has Hashimoto’s hypothyroidism (known to her or not!), or an already overtaxed/under-supported/under-nourished thyroid gland, her thyroid hormone levels are likely to decline further during pregnancy, due to the demands mentioned above.
Mothers with an undetected, mild thyroid dysfunction or subclinical hypothyroidism may suddenly find themselves with pronounced symptoms of hypothyroidism after becoming pregnant.
This again, highlights the importance of thorough thyroid testing: before, during and after pregnancy.
TESTING
Usually, just 1 thyroid test is done; TSH (thyroid stimulating hormone). This is not a thyroid hormone itself (!) but a hormone made in the pituitary gland in the brain and provides a level of ‘feedback; . Its name describes what it does (stimulates the thyroid) and will usually only be very high or very low in the case of marked underactivity or overactivity within the thyroid gland.
It still doesn’t tell us ‘how much’ thyroid hormone (mostly thyroxine [T4]) is being produced by the gland, or how well that T4 hormone is being converted to the biologically active thyroid hormone (T3), in the body.
Sometimes, TSH and T4 are tested. But again, this doesn’t show the full picture.
WHAT IS TESTED IN A COMPLETE THYROID BLOOD TEST?
A complete thyroid blood test includes:
TSH
T4
T3
Thyroid antibodies (Thyroid peroxidase [TPO} and thyroglobulin)
Reverse T3
Testing for thyroid antibodies is important! Having high thyroid antibodies during pregnancy (especially TPO) can lead to adverse obstetric outcomes, such as miscarriage and preterm birth. It’s also “significantly linked to the developing thyroid issues postpartum.” More about postpartum thyroiditis here.
Research shows that the “vast majority of women who develop postpartum thyroiditis are thyroid antibody positive prior to their pregnancy.” It’s important to mention here that there are various, evidence-based naturopathic and nutritional protocols to help reduce thyroid antibodies. Another reason why it’s important to test for thyroid antibodies, ideally before or in early pregnancy.
I check in on my pregnant client’s thyroid function via blood testing each trimester, and in the early weeks/months postpartum. Pregnant or not, thyroid issues rarely just appear overnight. They are often a result of long-term issues; commonly nutritional, adrenal, hormonal, blood sugar dysfunction, as well as pregnancies!
THYROID NUTRIENTS
The thyroid gland is a very nutrient-dependent gland. Therefore testing for these nutrient levels prior to, or in early pregnancy can provide the information required to ensure the thyroid is optimally supported through the ‘metabolic stress test’ of pregnancy.
I typically screen my preconception women for their nutrient levels of iodine, vitamin D, iron studies, zinc and selenium. Making changes to diet and/or supplements can help ensure the thyroid gland has an optimal supply of the nutrients it needs for the increased demands of pregnancy.