Last week I wrote about duabetes during pregnancy and how this gestational disorder can predict the development of the full blown disease later in life. A few weeks before this article, I wrote about preeclampsia, another pregnancy specific disease characterized by sudden onset of hypertension, protein in the urine and swelling. I stressed how preeclampsia can be associated with an increased future risk of hypertension and heart disease.
Now that you understand (from these previous blogs) that pregnancy sometimes serves as a "crystal ball" of future diseases in the mother, I want to give you another heads up. This time it's about thyroid disease.
Thyroid disease is an endocrinological disorder that often manifests itself initially during pregnancy. It is the second most common endocrine disorder for women of childbearing age. In the general population, approximately 4% to 10% of non-pregnant women have sub-clinical hypothyroidism.
What is subclinical hypothyroidism?
The production of thyroid hormone is regulated by the pituitary gland in the brain which secretes thyroid stimulating hormone (TSH). This hormone travels to the thyroid gland and stimulates the production of thyroid hormone. When a patient has increased TSH in conjunction with a thyroid hormone level within the normal range, this is often referred to as "subclinical hypothyroidism." It is generally considered to be an early stage of hypothyroidism. Overt hypothyroidism develops when a patient develops low thyroid hormone levels along with an elevated TSH level. The stress that pregnancy places on the entire body can cause a an improvement of an existing thyroid condition or cause a "silent" thyroid disease to reach a level at which it needs attention. This is often caused by antibodies developed by the body (auto-antibodies) against the organ. We are immediately concerned about this because women with latent thyroid disease during pregnancy have a higher risk of miscarriage in both the first and second trimester. Minor decreases in maternal thyroid levels have been associated with a lower IQ in the offspring. In addition, an association exists between pre-term delivery and thyroid abnormalities.
What are the changes that occur in pregnancy?
The thyroid gland sometimes increases in size during pregnancy. Iodide levels decrease during pregnancy because of fetal use of iodide. Therefore, it is recommended by the World Health Organization that pregnant women take 200 micrograms per day as a replacement.
The level of thyroid stimulating hormone is generally decreased in the first trimester, which has minimal clinical effects. TSH levels then normalize by second trimester.
How does preeclampsia effect the thyroid gland?
There is new consideration being given to the possibility that vascular damage after preeclampsia may affect the thyroid gland causing subclinical hypothyroidism. It has been proposed that this may be independent of the autoimmune process to which hypothyroidism is usually attributed.
In preeclampsia, the serum concentration of thyroid stimulating hormone is increased. This may cause subclinical hypothyroidism. Studies have shown that TSH levels sometimes increase 2.42 times above baseline in women with preeclampsia. Studies of women with preeclampsia have shown that those women are also more likely than a control group of women who do not have preeclampsia, to develop a raised TSH concentration about 20 years later. This raises the possibility that subclinical hypothyroidism is more common after preeclampsia and that women with a history of preeclampsia may even have an elevated risk of reduced thyroid function as they get older.
These thyroid findings may also contribute to the hypertension and coronary artery disease that has been found to occur in people who have had preeclampsia. Treatment with thyroxine may possibly reduce future cardiovascular risk. It may be advisable to screen women who have had preeclampsia for thyroid function after they deliver, with ongoing follow-ups. Treatment with thyroxine may prove to be beneficial in the prevention of early cardiovascular disease in affected women.
SUMMARY:
Preeclampsia can cause reduced thyroid function during pregnancy and can be an indicator of which women would be more prone to developing reduced thyroid function in later years. Women who have had preeclampsia are advised to be followed by the their physicians after their pregnancy has ended.
Stay healthy, all you mothers out there! Pay attention to what your pregnancy tells you.
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