Thyroid Pregnancy

Question 0

First, maternal total or bound thyroid hormone levels increase with serum concentration of thyroid-binding globulin. Second, the level of thyrotropin (also known as thyroid-stimulating hormone [TSH]), which plays a central role in screening for and diagnosis of many thyroid disorders, decreases in early pregnancy because of weak stimulation of TSH receptors caused by substantial quantities of human chorionic gonadotropin (hCG) during the first 12 weeks of gestation.

Answer 0

T

Question 1

Maternal thyroid volume is 30% larger in the third trimester than in the first trimester (1). In addition, there are changes to thyroid hormone levels and thyroid function throughout pregnancy.

Answer 1

True

Question 2

Physiologic thyroid changes during pregnancy are considerable and may be confused with maternal thyroid abnormalities. Maternal thyroid volume is 30% larger in the third trimester than in the first trimester (1). In addition, there are changes to thyroid hormone levels and thyroid function throughout pregnancy. Table 1 depicts how thyroid function test results change in normal pregnancy and in overt and subclinical thyroid disease. First, maternal total or bound thyroid hormone levels increase with serum concentration of thyroid-binding globulin. Second, the level of thyrotropin (also known as thyroid-stimulating hormone [TSH]), which plays a central role in screening for and diagnosis of many thyroid disorders, decreases in early pregnancy because of weak stimulation of TSH receptors caused by substantial quantities of human chorionic gonadotropin (hCG) during the first 12 weeks of gestation. Thyroid hormone secretion is thus stimulated, and the resulting increased serum free thyroxine (T4) levels suppress hypothalamic thyrotropin-releasing hormone, which in turn limits pituitary TSH secretion. After the first trimester, TSH levels return to baseline values and progressively increase in the third trimester related to placental growth and production of placental deiodinase (2). These physiologic changes should be considered when interpreting thyroid function test results during pregnancy (Table 1).

Answer 2

T

Question 3

Maternal T4 is transferred to the fetus throughout the entire pregnancy and is important for normal fetal brain development.

Answer 3

T

Question 4

Hyperthyroidism is characterized by a decreased TSH level and an increased free T4 level (Table 1).

Answer 4

Decrease tsh

Increased free t4

Question 5

Hyper-thyroidism occurs in 0.2% of pregnancies; Graves disease accounts for 95% of these cases

Answer 5

Graves’ disease accounts 95%

Question 6

The signs and symptoms of hyperthyroidism include

Answer 6

nervousness, tremors, tachycardia, frequent stools, excessive sweating, heat intolerance, weight loss, goiter, insomnia, palpitations, and hypertension

Question 7

Distinctive symptoms of Graves disease are

Answer 7

ophthalmopathy (signs include lid lag and lid retraction) and dermopathy (signs include localized or pretibial myxedema).

Question 8

Inadequately treated maternal thyrotoxicosis is associated with a greater risk of severe preeclampsia and maternal heart failure than treated, controlled maternal thyrotoxicosis

Answer 8

True

Question 9

*The level of TSH decreases in early pregnancy because of weak TSH receptor stimulation due to substantial quantities of human chorionic gonadotropin during the first 12 weeks of gestation. After the first trimester, TSH levels return to baseline values.

Answer 9

T

Question 10

Overt hyperthyroidism

Answer 10

Tsh decrease

Free t4 increase

Question 11

Subclinical hyperthyroidism Decrease No change

Answer 11

Tsh decrease

Free t4 no change

Question 12

Overt hypothyroidism Increase Decrease

Answer 12

Tsh increase

Free t4 decrease

Question 13

Subclinical hypothyroidism Increase No change

Answer 13

Tsh increase

Free t4 no change

Question 14

Inadequately treated hyperthyroidism is associated with an increase in

Answer 14

medically indicated preterm deliveries, low birth weight, and possibly fetal loss

Question 15

In most cases of maternal hyperthyroidism, the neonate is euthyroid. Fetal and neonatal risks associated with Graves disease are related either to the disease itself or to thioamide treatment of the disease.

Answer 15

T

Question 16

large proportion of thyroid disease in women is mediated by antibodies that cross the placenta, there is a legitimate concern about the risk of development of immune-mediated hypothyroidism and hyperthyroidism in the neonate.

Answer 16

T

Question 17

Pregnant women with Graves disease can have thyroid-stimulating immunoglobulin and TSH-binding inhibitory immunoglobulins, also known as thyrotropin-binding inhibitory immunoglobulins, that can stimulate or inhibit the fetal thyroid, respectively.

Answer 17

T

Question 18

. In some cases, maternal TSH-binding inhibitory immunoglobulins may cause transient hypothyroidism in neonates of women with Graves disease

Answer 18

T

Question 19

1–5% of these neonates have hyperthyroidism or neonatal Graves disease caused by the transplacental passage of maternal thyroid-stimulating immunoglobulin

Answer 19

T but incidence is low because of the balance of stimulatory and inhibitory antibodies as well as thioamide treatment

Question 20

The possibility of fetal thyrotoxicosis should be considered in all women with a history of Graves disease (5). If fetal thyrotoxicosis is diagnosed, consultation with a clinician with expertise in such conditions is warranted.

Answer 20

The incidence of neonatal Graves disease is unrelated to maternal thyroid function. The neonates of women with Graves disease who have been treated surgically or with radioactive iodine-131 before pregnancy and whose mothers required no thioamide treatment are at higher risk of neonatal Graves disease because they lack suppressive thioamide

Question 21

Routine evaluation of fetal thyroid function, including fetal thyroid ultrasonographic assessment, umbilical cord blood sampling, or both, is not recommended (13, 14). However, because maternal hyperthyroidism can be associated with fetal hydrops, growth restriction, goiter, or tachycardia, fetal thyroid disease should be considered in the differential diagnosis in these cases, and consultation with an expert may be appropriate (15

Answer 21

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