Pregnancy and Thyroid Cancer

Question 1

What is the medical treatment of hyperthyroidism during pregnancy?

Answer 1

First trimester- Prophylthiouracil (PTU)- fewer birth defects and miscarriages

Methimazole- second/third trimesters

Question 2

How to monitor hypo/hyperthyroidism during pregnancy?

Answer 2

Serum Free T4 and TSH every month during pregnancy

Question 3

If you have a thyroid cancer, what to do for work-up during first trimester?

Answer 3

• serum calcitonin levels
• OBGYN - ultrasound each trimester tracking development of fetus
• TSH and T4 every month

Question 4

Surgical treatment of thyroid cancer during first trimester

Answer 4

• do not interrupt pregnancy

- surgery after delivery

Question 5

When is the safest time to operate during pregnancy? Surgical indications?

Answer 5

Second trimester

Discuss and consider surgery during second trimester if:

• medullary thyroid cancer
• tumour growth (>50%)
• evidence of LN mets

Question 6

Adjuvant therapy for thyroid cancer during pregnancy

Answer 6

if radioactive iodine therapy is indicated, should be provided when patient not breast feeding

Question 7

Management during second and third trimester

Answer 7

same as first trimester

Question 8

Why is RAI contraindicated during pregnancy and breastfeeding?

Answer 8

fetal thyroid tissue is functional by 10-12 weeks and could be destroyed by radioiodine, resulting in cretinism

receptors in breast tissue