Final-Thyroid and Pregnancy

Question 1

what effect does the pregnancy hormone hCG have on the thyroid?

Answer 1

hCG binds directly onto the thyroid to increase T4

Question 2

what does overt hypothyroidism mean?

Answer 2

elevated TSH (>2.5 mIU/L) and low T4
OR
extremely elevated TSH alone (> 10 mIU/L)

Question 3

name some risks for overt hypothyroidism

Answer 3

preeclampsia or gestational HTN
placental abruption
nonreassuring FHTs
preterm delivery
low birth WT
increase c-section rate
perinatal morbidity and mortality
neuropsychological and cognitive impairment
postpartum hemorrhage

Question 4

definition of subclinical hypothyroidism

Answer 4

TSH between 2.5-10 mIU/L with normal T4

majority of patients are in this category

Question 5

risks for subclinical hypothyroidism

Answer 5

unclear
some studies show increased risk for preterm delivery and/or PG loss
may have neuropsychological impairment

Question 6

MC cause of hypothyroidism in pregnant women is

Answer 6

Hashimoto’s thyroiditis

Question 7

___ antibodies are found in 50% of PG women with subclinical hypothyroidism

Answer 7

TPO antibodies

Question 8

TPO antibodies are found in ____ % of PG women with overt hypothyroidism

Answer 8

80%

Question 9

what percent of euthyroid TPO positive women will develop subclinical hypothyroidism by term if untreated?

Answer 9

20%

*rise in TSH occurs despite expected decrease in TPO antibodies

Question 10

treat euthyroid TPO positive women in PG?

Answer 10

yes i think so…?

Question 11

risks for Hashimoto’s thyroiditis

Answer 11

fetal loss, perinatal mortality
large for gestational age infants
spontaneous miscarriage 2-3 times higher
preterm birth is doubled

Question 12

for TPO positive women, what were the findings of miscarriage rates and preterm delivery rates for those treated with T4 and those NOT treated with T4?

Answer 12

treated with T4:
miscarriage rate: 3.5%
preterm deliver rate: 7%

NOT treated with T4:
miscarriage rate: 13.8%
preterm delivery rate: 22.4%

Question 13

Normal TSH levels in pregnancy

Answer 13

first trimester .1-2.5 mIU/L
second trimester .2-3.0 mIU/L
thirst trimester .3-3.0 mIU/L

Question 14

things to keep in mind while measuring TSH levels in PG

Answer 14

• decr. in early PG

- diurnal variation (by up to 50%), lowest in late afternoon and highest at bedtime

Question 15

measuring T4 levels in PG

Answer 15

• some advocate for using total T4 in stead of free T4 because of reliability (bound T4 can be incr. due to estrogen with a decr. in free T4)
• the recommendation is to use total T4 when free T4 is discordant with TSH

Question 16

total T4 levels are 1.5 X higher than in nonpregnant women due to

Answer 16

TBG excess

Question 17

is universal screening for hypothyroidism recommended in asymptomatic PG women?

Answer 17

no. targeted screening recommended.

Question 18

Screening for hypothyroidism in pregnancy

Answer 18

• Symptomatic
• From an area of known moderate to severe iodine insufficiency
• Family history of thyroid disease
• Personal history of thyroid disease
• TPOab+
• Type 1 diabetes
• History of preterm delivery or miscarriage
• History of head or neck radiation
• Morbid obesity (BMI>40)
• Infertility
• Age >30 years

Question 19

treatment of hypothyroidism in PG

Answer 19

• recommends levothyroxine
• recommends against dessicated or combo T3/T4 (no studies to show safety for use in pregnancy)
• generic meds have variation in bioavailability (stuff they are tableted with can affect absorption)

Question 20

dosing thyroid meds in PG in patient with preexisting hypothyroidism

Answer 20

• btwn 50-85% of women being treated with exogenous thyroid hormone need to incr. dosage during pregnancy
• recommendation to incr. dosage by approximately 25%-35% at confirmation of PG

Question 21

dosing in overt hypothyroidism in PG

Answer 21

• start Levothyroxine at close to full replacement doses (1.6 mcg/Kg body WT per day)
• Patients with TSH

Question 22

treatment of subclinical hypothyroidism?

Answer 22

treatment is controversial.

Question 23

monitoring throughout pregnancy

Answer 23

• Repeat laboratory testing every 4 weeks through the first half of pregnancy
• Repeat testing of TSH between 26 and 32 weeks

Question 24

monitoring Hashimoto’s thyroiditis

Answer 24

Euthyroid TPO positive women

• TSH should be measured every 4 weeks until 20 weeks
• TSH should be measured at least once during the third trimester
• Initiate T4 if TSH rises above the trimester specific reference range

Question 25

postpartum dosage changes

Answer 25

• Reduce dosage to patient’s preconception dose after delivery
• Check TSH at 6 weeks postpartum

Question 26

Postpartum thyroiditis

-definition and etiology

Answer 26

-Occurrence of thyroid dysfunction in the first postpartum year in women who were euthyroid prior to pregnancy
-Autoimmune disorder associated with the presence of thyroid antibodies (TPO and thyroglobulin antibodies), lymphocyte abnormalities, complement activation, increased levels of IgG, increased NK cell activity, specific HLA haplotypes
Thought to be the rebound of the immune system after the suppression of pregnancy

Question 27

classic picture of postpartum thyroiditis

Answer 27

• Transient thyrotoxicosis followed by transient hypothyroidism with a return to the euthyroid state by the end of the first postpartum year
• Thyrotoxic phase typically occurs between 2 and 6 months postpartum and is often missed
• Hypothyroid phase occurs from 3-12 months postpartum
• 10%-20% of cases result in permanent hypothyroidism; may be even as high as 50%

Question 28

symptoms of thyrotoxic phase? why is it often missed?

Answer 28

• heat intolerance, nervousness, palpitations

- masked by stressors of being a new mom, not sleeping, returning to work, etc

Question 29

monitoring postpartum thyroiditis

Answer 29

• TSH should be tested every 2 mo until 1 year postpartum
• Women who are symptomatic should either have their TSH level retested in 4-8 weeks or be started on levothyroxine
• Try a taper/discontinuation of therapy 6-12 months after initiation of levothyroxine
• Women with a history of PPT should have an annual TSH performed

Question 30

prevention of postpartum thyroiditis?

Answer 30

selenium was found to be effective in one trial

• significant decr in frequency of postpartum thyroid dysfunction
• decr TPOab levels during PG