Sun28November0333PM 41

Regarding hyperthyroidism in pregnancy, are the following statements true or false?

True / False

Hyperthyroidism is best treated with radio-active iodine Correct

Hyperthyroidism occurs in about 1 pregnancy in every 2,000 Incorrect answer selected

Carbimazole is absolutely contraindicated in breast feeding mothers Incorrect answer selected

Hyperthyroidism may be associated with IUGR Correct

Hyperthyroidism is usually due to Hashimoto's disease Correct

Explanation

The overactive thyroid is a much greater risk to mother and fetus than hypothyroidism.

It is also becoming apparent that 5-10% of women have thyroid dysfunction in the puerperium. T3 and T4 levels rise in the first trimester which may be related to HCG production, as it shares some sequence homology with TSH. The probable role of HCG is further backed up by the increased T3 and T4 levels associated with hyperemesis and hydatidiform moles.

The fetus does not have a properly functional pituitary-thyroid system until 20 weeks, but its development, particularly of its nervous system, needs thyroid hormones.

Graves' disease is the commonest cause of hyperthyroidism in pregnancy, and the incidence is roughly 1 in 500 to 1 in 2,000.

Radio-iodine is absolutely contraindicated in pregnancy due to the risk to the fetal thyroid.

The most appropriate treatment is carbimazole/PTU and as both drugs cross the placenta the minimal dose of each should be used so as to render the patient euthyroid. It needs careful monitoring of TFTs and dose adjustment.

Both carbimazole and PTU are excreted in small amounts in breast milk. Usually they are of no consequence and breast feeding is not absolutely contraindicated however it is obviously not ideal to take either whilst breastfeeding.