Thyroid Disease in Pregnancy

Question 1

When does fetal thyroid tissue begin to concentrate iodine and synthesize thyroid hormone?

Answer 1

12 weeks gestation

Question 2

Risks of untreated overt hypothryoidism

Answer 2

SAB
Stillbirth
Preterm birth
Placental abruption
Pre E
Low birth weight
Impaired neuropsychologic development

Question 3

Risks of hyperthyroidism?

Answer 3

Fetal thyrotoxicosis
Fetal tachycardia
Poor fetal growth
Pre E
Thryoid Storm/Heart Failure

Question 4

What are the maternal risks of Hyperthyroidism in pregnancy?

Answer 4

PRE E
HEART FAILURE (cardiomyopathy caused by the myocardial effects of excess T4)
Thyroid Storm

Question 5

Most common cause of hypothyroidism in pregnancy?

Answer 5

Hashimotos

Question 6

Treatment of hypothyroidism? Dose?

Answer 6

Levothyroxine (1.6 mcg/kg)

Adjust dose based on repeat labs 6 weeks later

Question 7

Hyperthyroidism is caused by what 95% of the time?

Answer 7

Graves Disease

Question 8

Treatment for hyperthyroidism throughout pregnancy?

Answer 8

Propylthiouracil = inhibits thyroid peroxidase 100 mg TID, continue to increase every 4 weeks until euthyroid

Monitor Free T4, want top of normal range

Less readily crosses placenta

Hepatotoxicity for Mom (rare)

Question 9

SE of Propylthiouracil?

Answer 9

risk of hepatotoxicity (rare)

Question 10

Treatment for hyperthyroidism in second/third trimester?

Answer 10

Methimazole = inhibits thyroid peroxidase

20 mg QD

Per ACOG, can now continue PTU throughout pregnancy

Question 11

SE of Methimazole if used in first trimester?

Answer 11

Aplasia Cutis = congenital syndrome characterized by the absence of skin on various areas of the body

Esophageal or Choanal atresia

Question 12

TSH and BHCG share which subunit?

Answer 12

alpha sub unit

TSH decreases in early pregnancy because of weak stimulation of TSH receptors caused by substantial quantities of hcg during first trimester

Thyroid hormone secretion is thus stimulated, and the resulting increased serum free T4 levels suppress TSH production

After first trimester > TSH levels return to baseline and progressively increase in the third trimester

Question 13

Which part of the pituitary gland produces TSH?

Answer 13

Anterior pituitary

Question 14

Recommended iodine intake in pregnancy?

Answer 14

220 mcg daily

Question 15

Is subclinical hyperthyroidism associated with adverse pregnancy outcomes?

Answer 15

NO!

Don’t treat it

Question 16

Is subclinical hypothyroidism associated with adverse pregnancy outcomes?

Answer 16

NO!

Don’t treat it

Question 17

Rare risk of PTU or methimazole that occurs in 10% of moms on these medications?

Answer 17

Leukopenia (no need to dc)

RARELY (1%) of the time progress to agranulocytosis - then must dc drugs

Question 18

What labs do you monitor for treatment of hyperthryoid?

Answer 18

Only monitor T4 (keep in normal to high range)

No need to get a TSH

Adjust meds accordingly and recheck in 2 weeks

Question 19

Recommended dose of Levothyroxine?

Answer 19

1.6 mcg/kg daily

Question 20

What labs do you get to monitor treatment for hypothyroidism?

Answer 20

TSH (NOT T4, which is opposite of hyperthyroid)

Check TSH Q4-6 weeks, adjust by 25-50 mcg until normal TSH

Goal TSH < 2.5

Question 21

In women with known thyroid disease, how much is their T4 requirement going to increase in pregnancy?

Answer 21

25% increase
For those with hx of thyroidectomy or radioiodine ablation

Question 22

Incidence of thyroid storm in pregnancy?

Answer 22

1-2%

Question 23

Fever
Tachycardia
Arrhythmias
Vomiting/diarrhea
CNS dysfunction

Develops abruptly
Leads to multi organ failure

Answer 23

Thyroid storm

Question 24

Is hyperthyroidism more likely to cause thyroid storm or thyrotoxic heart failure?

Answer 24

Heart failure! Occurs in 8% of women with uncontrolled hyPERthyroidism

Due to excess free T4 effects on myocardium

**usually precipitated by other diseases PreE, sepsis, anemia

Often reversible with treatment (treated the same as thyroid storm)

Question 25

Treatment for Thyroid storm or thyrotoxic heart failure in pregnancy

Answer 25

1. inhibit release of T3/T4 with PO PTU (1000 mg loading dose PO, then 200 mg Q6h)
2. Add back Iodine 1-2 hours after PTU (Lugol’s iodide 10 drops PO q8h)
3. Block peripheral conversion of T4 to T3 with DEXAMETHASONE
4. Symptom management/ Can control tachycardia w/ b blocker (however this may precipitate heart failure)

Question 26

Postpartum thyroiditis can occur in what time frame after delivery?

Answer 26

Within 12 months of delivery - can manifest as hyper/hypo or both

First hyperthryoid lasting a few months, following by hypothyroidism (usually between 4-8 months postpartum)

Usually requires replacement for 6-12 months

Question 27

What percentage of women will require permanent treatment for hypothyroidism after postpartum thyroiditis?

Answer 27

1/3 of women

Question 28

Work up of thyroid nodule in pregnancy?

Answer 28

H&P
TSH
Ultrasound
If imaging concerning for malignancy then FNA

**Radioiodine scanning is not recommended in pregnancy due to theoretical risk of fetal irradiation

If cancer is detected - discussion regarding treatment

Many times surgery is delayed until after delivery due to concern for potential removal of parathyroid gland

Question 29

What happens to Total T4/T3 during pregnancy?

Answer 29

Both increase due to increase in thyroid binding globulin (caused by estrogen)

Free T4/T3 are unchanged (except in early pregnancy when there is HCG effect)