Thyroid Disease in Pregnancy Flashcards
When does fetal thyroid tissue begin to concentrate iodine and synthesize thyroid hormone?
12 weeks gestation
Risks of untreated overt hypothryoidism
SAB
Stillbirth
Preterm birth
Placental abruption
Pre E
Low birth weight
Impaired neuropsychologic development
Risks of hyperthyroidism?
Fetal thyrotoxicosis
Fetal tachycardia
Poor fetal growth
Pre E
Thryoid Storm/Heart Failure
What are the maternal risks of Hyperthyroidism in pregnancy?
PRE E
HEART FAILURE (cardiomyopathy caused by the myocardial effects of excess T4)
Thyroid Storm
Most common cause of hypothyroidism in pregnancy?
Hashimotos
Treatment of hypothyroidism? Dose?
Levothyroxine (1.6 mcg/kg)
Adjust dose based on repeat labs 6 weeks later
Hyperthyroidism is caused by what 95% of the time?
Graves Disease
Treatment for hyperthyroidism throughout pregnancy?
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)
SE of Propylthiouracil?
risk of hepatotoxicity (rare)
Treatment for hyperthyroidism in second/third trimester?
Methimazole = inhibits thyroid peroxidase
20 mg QD
Per ACOG, can now continue PTU throughout pregnancy
SE of Methimazole if used in first trimester?
Aplasia Cutis = congenital syndrome characterized by the absence of skin on various areas of the body
Esophageal or Choanal atresia
TSH and BHCG share which subunit?
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
Which part of the pituitary gland produces TSH?
Anterior pituitary
Recommended iodine intake in pregnancy?
220 mcg daily
Is subclinical hyperthyroidism associated with adverse pregnancy outcomes?
NO!
Don’t treat it
Is subclinical hypothyroidism associated with adverse pregnancy outcomes?
NO!
Don’t treat it
Rare risk of PTU or methimazole that occurs in 10% of moms on these medications?
Leukopenia (no need to dc)
RARELY (1%) of the time progress to agranulocytosis - then must dc drugs
What labs do you monitor for treatment of hyperthryoid?
Only monitor T4 (keep in normal to high range)
No need to get a TSH
Adjust meds accordingly and recheck in 2 weeks
Recommended dose of Levothyroxine?
1.6 mcg/kg daily
What labs do you get to monitor treatment for hypothyroidism?
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
In women with known thyroid disease, how much is their T4 requirement going to increase in pregnancy?
25% increase
For those with hx of thyroidectomy or radioiodine ablation
Incidence of thyroid storm in pregnancy?
1-2%
Fever
Tachycardia
Arrhythmias
Vomiting/diarrhea
CNS dysfunction
Develops abruptly
Leads to multi organ failure
Thyroid storm
Is hyperthyroidism more likely to cause thyroid storm or thyrotoxic heart failure?
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)
Treatment for Thyroid storm or thyrotoxic heart failure in pregnancy
- inhibit release of T3/T4 with PO PTU (1000 mg loading dose PO, then 200 mg Q6h)
- Add back Iodine 1-2 hours after PTU (Lugol’s iodide 10 drops PO q8h)
- Block peripheral conversion of T4 to T3 with DEXAMETHASONE
- Symptom management/ Can control tachycardia w/ b blocker (however this may precipitate heart failure)
Postpartum thyroiditis can occur in what time frame after delivery?
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
What percentage of women will require permanent treatment for hypothyroidism after postpartum thyroiditis?
1/3 of women
Work up of thyroid nodule in pregnancy?
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
What happens to Total T4/T3 during pregnancy?
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)
