Thyroid

Question 1

Changes in physiology

Answer 1

1. Increase in serum thyroxine binding globulin (TBG)
2. Increase in total T4 and T3 (plateaus ~ 20 weeks)

Question 2

HCG and thyroid fx

Answer 2

1. Serum hCG increases
2. Serum FT4 and FT3 concentrations increase slightly, usually within the normal range 3. Serum TSH concentrations are appropriately reduced.
3. As hCG secretion declines, serum free T4 and T3 concentrations decline and serum TSH concentrations rise slightly to or within the normal range.

Question 3

Normal pregnancy levels (when using nonpregnancy reference ranges)

Answer 3

1. TSH 0.1 to 4 (7-12 wks)
2. FT4 3. FT3

Question 4

What to order

Answer 4

• TSH
  ●If the serum TSH is >2.5 mU/L, measure TPO antibodies.
  ●If the TSH is >4 mU/L, measure free T4
  -If TSH is low, measure FT3
• total T4/T3 if pregnancy reference ranges aren’t available and results seem discordant

Question 5

Iodine requirements in pregnancy and lactation

Answer 5

250 mcg of iodine daily

Question 6

Dangers of deficiency

Answer 6

Neurological deficits

Question 7

Hyperthyroidism (definition)

Answer 7

Serum TSH: suppressed (<0.1 mU/L) or undetectable (<0.01 mU/L) and elevated thyroid hormone levels that exceed the reference ranges for pregnancy.

Question 8

Causes of hyperthyroidism

Answer 8

1. HCG mediated (temporary) 2. Graves disease

Question 9

Treatment of hyperthyroidism

Answer 9

Most women are treated with thionamides.

Question 10

Hypothyroidism (causes)

Answer 10

iodine deficiency or chronic autoimmune (Hashimoto’s) thyroiditis

Question 11

Hypothyroidism (definition)

Answer 11

Elevated TSH
Low T4

Question 12

Dangers of thyroid antibodies

Answer 12

Pregnancy loss, developing subclinical hypothyroidism

Question 13

Who to screen

Answer 13

●Living in an area of moderate to severe iodine insufficiency
●Symptoms of hypothyroidism
●Family or personal history of thyroid disease
●Personal history of:
*Thyroid peroxidase (TPO) antibodies
*Goiter
*Age >30 years
*Type 1 diabetes
*Head and neck irradiation
*Recurrent miscarriage or preterm delivery
*Multiple prior pregnancies (two or more)
*Morbid obesity ( [BMI] ≥40 kg/m2)
*Infertility
*Prior thyroid surgery
*Use of amiodarone, lithium, or recent administration of iodinated radiologic contrast agents

Question 14

PP Thyroiditis

Question 15

Treatment for hypothyroidism

Question 16

Treatment for hyperthyroidism

Question 17

TSH Pregnancy ranges

Answer 17

First trimester 0.26-2.66
Second trimester 0.55-2.73
Third trimester 0.43-2.91