Thyroid Function In Pregnancy

Question 1

What are the five factors that alter thyroid function in pregnancy?

Answer 1

1. Transient increase in h h during the first tri - really stimulates the TSH-R
2. Estrogen-induced rise in TBG during the first tri which is sustained during pregnancy
3. Alterations in the immune system, leading to the onset, exacerbation or amelioration of an underlying autoimmune thyroid disease
4. Increased thyroid hormone metabolism by the placenta
5. Increased urinary iodide excretion, which can cause impaired thyroid hormone production in areas of marginal iodine sufficiency

Question 2

Hcg-induced changes in thyroid function can result in transient gestational hyperthyroidism that may be associated with what?

Answer 2

Hyperemesis gravidarum

Question 3

How many times higher are t4 and t3 levels are in pregnancy ?

Answer 3

Total t4 and t3 are about 1.5x higher throughout pregnancy but the free T4 progressively decreases so that 3rd trimester values in healthy pregnancies are often below the nonpregnant lower reference cutoff

Question 4

When is targeted TSH testing recommended for women planning pregnancy?

Answer 4

1. If they have STRONG FAMILY HISTORY of AI THYROID DISEASE, other AI disorders (eg type 1 diabetes), infertility
2. Prior preterm delivery or recurrent miscarriage, signs or symptoms of thyroid disease, older than 30 years
3. Thyroid hormone requirements are increased by up to 45% during pregnancy in LT4-treated hypothyroidism