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What You Wonder About Thyroid Diseases (Goiter) During Pregnancy


Thyroid hormone is essential for normal pregnancy and fetal development.

The thyroid gland of the fetus does not mature functionally until the 18th-20th week of pregnancy. For this reason, it depends on the thyroid hormone levels of the mother, who crossed the placenta at this stage.

Therefore, maternal thyroid dysfunctions can lead to adverse pregnancy outcomes such as miscarriage, growth restriction, hypertensive disorders, preterm delivery, and increase the risk of low IQ in the newborn.


Hypothyroidism, that is, the inability of the thyroid gland to produce enough hormones, is seen in 3% of all pregnant women. Although signs such as fatigue, weight gain, decreased exercise capacity and constipation are frequently seen during pregnancy, most of the pregnant women have no complaints.



The thyroid gland cannot perform its ideal function in iodine deficiency. Türkiye is located in the moderate iodine deficiency region. Perchlorate, nitrate and thiocyanate are substances that impair iodine uptake. Thiocyanate is found in cigarette smoke. Perchlorate is found in solid rocket fuels, fireworks, explosives and nitrate fertilizers. Nitrate is also found in vegetables, packaged meat products containing preservatives, and drinking water. Thyroid functions are further suppressed in pregnant women exposed to substances such as perchlorate, nitrate and thiocyanate with low iodine intake.


During pregnancy and lactation, women's daily iodine intake should be 250 mcg/day. Assuming that a pregnant woman consuming iodized table salt in Turkey takes 100-150 mcg/day of iodine on average, 100-150 mcg/day iodine supplement should be given to all pregnant women. This amount should be 200 mcg/day in pregnant women who have salt restriction.


Since Turkey is a region of iodine deficiency and thyroid hormone deficiency has the risk of causing many negative consequences during pregnancy, TSH measurement should be performed initially in all women who are planning to become pregnant and in all pregnant women.


TSH levels below 2.5 mIU/ml in the first trimester; in the second trimester and in the third trimester, it should be below 3 mIU/ml. Apart from these values, the pregnant woman should be started on medication containing thyroid hormone. TSH checks are repeated at intervals of 4-6 weeks in the first 20 weeks, then at 26-28 weeks and 32-34 weeks afterward.

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