Nowadays, thyroid function has become a routine examination item for women of childbearing age during pregnancy preparation and pregnancy. This is the main reason why a large proportion of patients who visit endocrinology clinics are pregnancy hypothyroidism patients.
Case:
A young expectant mother asked me with her test results: "Doctor, are there any abnormalities in my test?"
I asked her about her pregnancy period and replied: "It is pregnancy-induced hypothyroidism and she needs to take a dose." A thyroid hormone preparation, Euthyrox. "
" Will taking Euthyrox have no effect on the fetus? "
" If the dose is appropriate, there will be no effect. "
Seeing her doubts, I strengthened my tone: " During pregnancy, you should insist on taking the medicine, check it regularly, and decide to increase or decrease the dosage based on the test results. Do not reduce or stop using any medicine at will because of your subjective opinion. Do you know why you should do this? Hypothyroidism affects fetal brain development. ”
Hypothyroidism in pregnancy affects fetal brain development and is related to the physiological effects of thyroid hormone , the source of fetal thyroid hormone and the characteristics of brain growth and development.
Thyroid hormone plays a role mainly by regulating the rate of cell differentiation and gene expression. During the fetal period and early postnatal period, thyroid hormone binds to thyroid hormone receptors in different brain areas and regulates the expression of specific genes in these brain areas.
Thyroid hormone deficiency affects neurogenesis, neuronal and glial cell differentiation and migration, synaptic generation and myelin formation, causing brain development retardation, intellectual disability and neurological damage .
In the first trimester, that is, from the first week to the twelfth week of pregnancy, thyroid hormone can be found in the body cavity fluid of the 16-week-old fetus. This time is much earlier than the time when fetal thyroid begins to secrete thyroid hormone. By 10-16 weeks of age , thyroid hormone and nuclear receptors for thyroid hormone have increased 6-10 times.
The thyroid hormone found in the fetus during the first trimester may come from the mother all or most of it. Therefore, babies born to women with lower than normal thyroid hormone levels during early pregnancy had lower mental development scores.
In the 24th week of pregnancy, the fetal thyroid gland begins to secrete thyroid hormone. Thereafter, fetal thyroid hormones come essentially, but not exclusively, from the fetus itself; there is still significant transfer of thyroid hormone from the mother to the fetus during the third trimester.
The characteristics of fetal and newborn brain growth and development are that there are two periods of fastest growth.
The first period is between the third and fifth months of pregnancy. This period is a critical period for neuronal proliferation and migration and the formation of neuronal tissue.
The second period begins in the third trimester of pregnancy and lasts until the second and third years after birth. This period is a critical period for glial cell proliferation, migration, and myelination .
What expectant mothers need to pay special attention to is that the first critical period of fetal brain growth and development occurs before the fetal thyroid gland has no thyroid hormone secretion function, and the thyroid hormones it needs almost entirely come from the mother. In the second critical period, although the fetus can synthesize and secrete thyroid hormone, a considerable amount of the thyroid hormone it needs still comes from the mother.
Now that you understand the rationale behind monitoring thyroid function during pregnancy and taking an appropriate amount of Euthyrox when suffering from gestational hypothyroidism, what will you do?
