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Practice bulletins > #223 Thyroid Disease in Pregnancy > Flashcards

#223 Thyroid Disease in Pregnancy Flashcards

1
Q

How does maternal thyroid volume change during pregnancy?

A

Increases 10-30% during 3rd trimester, attributable to increases in extracellular fluid and blood volume during pregnancy

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2
Q

How does maternal total or bound thyroid hormone levels change in pregnancy?

A

Increases

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3
Q

How does maternal serum concentration of thyroid-binding globulin change during pregnancy?

A

Increases

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4
Q

How does the level of thyrotropin (AKA TSH) change in early pregnancy?

A

Decreases

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5
Q

Why does TSH decrease in early pregnancy?

A

Due to weak stimulation of TSH receptors by substantial quantities of hCG during first 12 weeks

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6
Q

What is the maternal status if TSH is decreased and Free T4 is Increased?

A

Overt hyperthyroidism

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7
Q

What is the maternal status if TSH is decreased and Free T4 has no change?

A

Subclinical hyperthyroidism

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8
Q

What is the maternal status if TSH is increased and Free T4 is decreased?

A

Overt hypothyroidism

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9
Q

What is the maternal status if TSH is increased and Free T4 has no change?

A

Subclinical hypothyroidism

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10
Q

How does the normal range of TSH change in late first trimester of pregnancy?

A

Lower limit reduced by 0.4mu/L and upper limit by 0.5mu/L.

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11
Q

How does the normal range of TSH change in 2nd trimester? Third?

A

No change, can use standard reference range

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12
Q

How does the reference range for total T4 and total T3 be changed after 16wks pregnancy?

A

Upper limit can be increased by 50%.

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13
Q

When does the fetal thyroid gland begin concentrating iodine and synthesizing thyroid hormone?

A

At approximately 12wks

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14
Q

Approximately what % of T4 in umbilical cord serum at delivery is maternal in origin?

A

30%

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15
Q

True or false, maternal T4 is important in normal fetal brain development

A

True

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16
Q

Regarding maternal thyroid disorder, what should be communicated to neonatologist/pediatrician?

A

Use of propylthiouracil, methimazole, hx of known maternal thyroid receptor antibodies (can affect neonatal thyroid function)

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17
Q

What % of pregnancies are complicated by hyperthyroidism?

A

0.2-0.7%

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18
Q

What % of hyperthyroidism cases in pregnancy are caused by Grave’s dx?

A

95%

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19
Q

What are the signs and symptoms of hyperthyroidism?

A

Nervousness, tremors, tachycardia, frequent stools, excessive sweating, heat intolerance, weight loss, goiter, insomnia, palpitations, HTN

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20
Q

What are distinctive features of Graves dx?

A

Ophthalmopathy (lid lag and lid retraction) and dermopathy (localized or pretibial myxedema)

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21
Q

What is inadequately treated maternal thyrotoxicosis associated with?

A

Greater risk of preeclampsia with SF, maternal heart failure, and thyroid storm

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22
Q

What is inadequately treated hyperthyroidism associated with in pregnancy?

A

Increase in medically indicated preterm deliveries, low birth weight, miscarriage, and stillbirth

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23
Q

How does fetal thyrotoxicosis typically manifest?

A

Fetal tachycardia and poor fetal growth

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24
Q

True or false, Graves disease can lead to neonatal hyper and hypothyroidism?

A

True. Thyroid stimulated immunoglobulin (neonate hyperthyroid) vs TSH-binding inhibitory immunoglobulins (neonate hypothyroid)

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25
Q

What % of neonates born to mothers with Graves dx will have hyperthyroidism or neonatal Graves dx?

A

1-5%

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26
Q

Subclinical hyperthyroidism is reported in what % of pregnant women?

A

0.8-1.7%

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27
Q

Is subclinical hyperthyroidism associated with adverse pregnancy outcomes?

A

No

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28
Q

Should you treat pregnant women with subclinical hyperthyroidism?

A

Not recommended, no benefit to mom or fetus

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29
Q

What # out of 1,000 pregnancies are complicated by overt hypothyroidism?

A

2-10 out of 1,000

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30
Q

What are common signs and symptoms of hypothyroidism?

A

Fatigue, constipation, cold intolerance, muscle cramps, and weight gain. Other clinical findings include edema, dry skin, hair loss, and a prolonged relaxation phase of deep tendon reflexes. Goiter may or may not be present

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31
Q

What is the most common cause of hypothyroidism in pregnancy?

A

Hashimoto thyroiditis

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32
Q

What characterizes Hashimoto thyroiditis (mechanism of disease)?

A

Glandular destruction by autoantibodies, particularly antithyroid peroxidase antibodies

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33
Q

What antibodies are associated with Hashimoto thyroiditis?

A

Antithyroid peroxidase antibodies

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34
Q

What is the recommended daily dietary intake of iodine in pregnant and lactating women?

A

220mcg in pregnant women. 290mcg in lactating women.

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35
Q

What adverse perinatal outcomes are associated with untreated overt hypothyroidism?

A

Spontaneous abortion, preeclampsia, preterm birth, abruptio placentae, stillbirth

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36
Q

True or false, adequate thyroid hormone replacement in overt hypothyroidism minimizes the risk of adverse outcomes?

A

True

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37
Q

What fetal and neonatal effects are associated with untreated maternal hypothyroidism?

A

Increased risk of low birth weight and impaired neuropsychologic development

38
Q

What is the prevalence of fetal hypothyroidism in the offspring of women with Hashimoto thyroiditis (1 in how many)?

A

only 1 in 180,000

39
Q

What is the prevalence (%) of subclinical hypothyroidism in pregnancy?

A

2-5%

40
Q

Does treatment of subclinical hypothyroidism during pregnancy improve outcomes?

A

No evidence to support

41
Q

Is universal screening for thyroid disease in pregnancy recommended?

A

No

42
Q

When should you test a pregnant women for thyroid disorders?

A

Women with a personal or family hx of thyroid disease, type 1 DM, or clinical suspicion of thyroid disease.

43
Q

What is the first line screening test to assess thyroid status in pregnancy?

A

TSH level

44
Q

If TSH is elevated in pregnancy, what is the next test that should be done?

A

Free T4

45
Q

If TSH is decreased in pregnancy, what is the next test that should be done?

A

Free T4 and total T3

46
Q

Why measure total T3 rather than free T3?

A

Assays for estimating free T3 are less robust than those measuring free T4.

47
Q

What value(s) should be monitored and used to dictate therapy in pregnant with with hyperthyroidism?

A

Adjust drug to achieve a free T4 at upper end of the normal pregnancy range. If also have T3 thyrotoxicosis, total T3 should be monitored with goal at upper end of normal pregnancy range.

48
Q

What category of medication are propylthiouracil or methimazole?

A

Thioamides (treat hyperthyroidism)

49
Q

What thioamide is typically avoided in first trimester and why?

A

Methimazole. Associated with rare embryopathy characterized by esophageal or choanal atresia as well as aplasia cutis

50
Q

What medication is generally preferred for treatment of hyperthyroidism in first trimester?

A

Propylthiouracil

51
Q

After first trimester, which medication should be used for hyperthyroidism?

A

Either methiazole or propylthiouracil. In rare cases, PTU results in clinically significant hepatotoxicity prompting transition.

52
Q

What is a concern about transitioning from propylthiouracil to methimazole after first trimester?

A

A period of poor control of hyperthyroidism

53
Q

What medication is preferred for T3-predominant thyrotoxicosis? Why?

A

Propylthiouracil, decreases T4 to T3 conversion

54
Q

What is the conversion of propylthiouracil to methimazole?

A

Ratio of 20:1 PTU to methimazole

55
Q

Transient leukopenia occurs in up to what % of pregnant women who take thioamide drugs? Does this require drug cessation?

A

10%. No.

56
Q

What % of patients who take thioamide drugs get agranulocytosis? Does this require drug cessation?

A

Less than 1%. Yes.

57
Q

Is development of agranulocytosis with thioamide drugs dose-related?

A

No

58
Q

Should serial leukocyte counts be performed during thioamide administration?

A

No. Agranulocytosis is acute onset so serial leukocyte counts during therapy are not helpful

59
Q

What is the dosage of propylthiouracil?

A

100-600mg daily, divided into three doses, PO. Typical dose is 200-400mg daily.

60
Q

What is the dosage of methimazole?

A

5-30mg orally daily, divided into two doses (may be reduced to one daily dose as maintenance therapy is established)

61
Q

What medication is preferred for symptomatic palpitations in pregnant patients with hyperthyroidism? What dosing?

A

Propranolol. 10-40mg taken 3-4x/daily

62
Q

What is the recommendation for initial dose of T4 in pregnancy?

A

1-2mcg/kg daily (approximately 100mcg daily), may require larger doses if prior thyroidectomy or radioiodine therapy

63
Q

What lab value guides treatment of hypothyroidism in pregnancy?

A

TSH value

64
Q

What is the goal TSH level when treating hypothyroidism in pregnancy?

A

TSH goal between lower limit of reference range and 2.5mu/L.

65
Q

How often should TSH be evaluated while adjusting thyroid hormone medication?

A

Every 4-6wks

66
Q

Should thyroid hormone medication be adjusted in early pregnancy?

A

Can do anticipatory 25% increases in T4 replacement at pregnancy confirmation

67
Q

What % of reproductive-aged women will have autoantibodies to thyroid peroxidase and thyroglobulin?

A

Up to 20%. Most test euthyroid

68
Q

Transient biochemical features of hyperthyroidism may be observed in what % of women in early pregnancy?

A

3-11%

69
Q

What are causes of gestational transient hyperthyroidism (aka physiologic hyperthyroidism)?

A

Multiple gestation or molar pregnancy, for example

70
Q

Are women with gestational transient hyperthyroidism typical symptomatic?

A

No

71
Q

Do women with gestational transient hyperthyroidism require treatment?

A

Not been shown to be beneficial, not recommended. Not associated with poor pregnancy outcomes.

72
Q

Are measurements of thyroid function recommended for patients with hyperemesis gravidarum?

A

Not unless other signs of overt hyperthyroidism are evident

73
Q

How does thyroid storm typically manifest?

A

Combination of the following signs and symptoms: fever, tachycardia, cardiac dysrhythmia, and CNS dysfunction

74
Q

Is thyroid storm or cardiomyopathy from hyperthyroidism more common in pregnancy?

A

Cardiomyopathy

75
Q

What % of pregnant women with uncontrolled hyperthyroidism develop heart failure and pulmonary HTN from cardiomyopathy d/t excessive T4?

A

9%

76
Q

True or false, T4-induced cardiomyopathy and pulmonary HTN are reversible?

A

True

77
Q

If thyroid storm or thyrotoxic heart failure is suspected, what lab values should be checked?

A

Serum free T4, total T3, and TSH levels

78
Q

What is the medical management of thyroid storm or thyrotoxic heart failure in pregnancy?

A
  • Inhibit thyroid release of T3 and T4 (PTU 1000mg PO then 200mg q6h); iodine administration 1-2h after pTU.
  • Further block peripheral conversion of T4 to T3 (dexamethasone or hydrocortisone)
  • Propanolol, labetalol, or esmolol (caution in setting of heart failure)
  • Supportive measures as needed
79
Q

When should a diagnosis of fetal thyrotoxicosis be considered in cases of maternal hyperthyroidism?

A

Fetal hydrops, growth restriction, fetal goiter, or persistent fetal tachycardia

80
Q

Thyroid nodules are found in what % of reproductive-aged women?

A

1-2%, with prevalence increasing with age

81
Q

What is the initial work up of a pregnant woman with a thyroid nodule?

A

Complete H&P, serum TSH testing, ultrasound of the neck

82
Q

What % of solitary thyroid nodules are benign?

A

90-95%

83
Q

What ultrasound characteristics of thyroid nodules are associated with malignancy?

A

Hypoechoic pattern, irregular margins, and microcalcifications. When all 3 present, these features correlate with a malignancy risk exceeding 70%

84
Q

If thyroid nodule in pregnancy concerning for possible malignancy, what is the next step?

A

Fine-needle aspiration

85
Q

Is radioiodine scanning in pregnancy allowed?

A

Not recommended because of theoretical risk associated with fetal irradiation

86
Q

What is typical management for a women with thyroid cancer diagnosed in 1st or 2nd trimester?

A

Thyroidectomy may be performed before 3rd trimester, but concerning for inadvertent removal of parathyroid glands often leads to delay postpartum.

87
Q

What is the typical management for a women with thyroid cancer diagnosed in 3rd trimester?

A

Deferred to immediate postpartum period

88
Q

How is postpartum thyroiditis defined?

A

Thyroid dysfunction within 12 months of delivery (hyper, hypo, or both)

89
Q

Transient autoimmune thyroiditis is found in what % of women during first year after childbirth?

A

5-10%

90
Q

What are the two clinical phases in classical postpartum thyroiditis?

A

New-onset abnormal TSH and free T4

  1. Destruction-induced thyrotoxicosis (small, painless goiter) usually lasts few months
  2. Overt hypothyroidism that occurs between 4-8 months postpartum and thyromegaly
91
Q

What are the outcomes of postpartum thyroiditis?

A

Most resolve spontaneously. Approximately 1/3 will eventually develop permanent, overt hypothyroidism. Annual progression rate is 3.6%

92
Q

True or false, presence of thyroid autoantibodies increases the risk of women with postpartum thyroiditis developing permanent hypothyroidism

A

True

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