Final-Thyroid and Pregnancy Flashcards
what effect does the pregnancy hormone hCG have on the thyroid?
hCG binds directly onto the thyroid to increase T4
what does overt hypothyroidism mean?
elevated TSH (>2.5 mIU/L) and low T4
OR
extremely elevated TSH alone (> 10 mIU/L)
name some risks for overt hypothyroidism
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
definition of subclinical hypothyroidism
TSH between 2.5-10 mIU/L with normal T4
majority of patients are in this category
risks for subclinical hypothyroidism
unclear
some studies show increased risk for preterm delivery and/or PG loss
may have neuropsychological impairment
MC cause of hypothyroidism in pregnant women is
Hashimoto’s thyroiditis
___ antibodies are found in 50% of PG women with subclinical hypothyroidism
TPO antibodies
TPO antibodies are found in ____ % of PG women with overt hypothyroidism
80%
what percent of euthyroid TPO positive women will develop subclinical hypothyroidism by term if untreated?
20%
*rise in TSH occurs despite expected decrease in TPO antibodies
treat euthyroid TPO positive women in PG?
yes i think so…?
risks for Hashimoto’s thyroiditis
fetal loss, perinatal mortality
large for gestational age infants
spontaneous miscarriage 2-3 times higher
preterm birth is doubled
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?
treated with T4:
miscarriage rate: 3.5%
preterm deliver rate: 7%
NOT treated with T4:
miscarriage rate: 13.8%
preterm delivery rate: 22.4%
Normal TSH levels in pregnancy
first trimester .1-2.5 mIU/L
second trimester .2-3.0 mIU/L
thirst trimester .3-3.0 mIU/L
things to keep in mind while measuring TSH levels in PG
- decr. in early PG
- diurnal variation (by up to 50%), lowest in late afternoon and highest at bedtime
measuring T4 levels in PG
- 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
total T4 levels are 1.5 X higher than in nonpregnant women due to
TBG excess
is universal screening for hypothyroidism recommended in asymptomatic PG women?
no. targeted screening recommended.
Screening for hypothyroidism in pregnancy
- 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
treatment of hypothyroidism in PG
- 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)
dosing thyroid meds in PG in patient with preexisting hypothyroidism
- 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
dosing in overt hypothyroidism in PG
- start Levothyroxine at close to full replacement doses (1.6 mcg/Kg body WT per day)
- Patients with TSH
treatment of subclinical hypothyroidism?
treatment is controversial.
monitoring throughout pregnancy
- Repeat laboratory testing every 4 weeks through the first half of pregnancy
- Repeat testing of TSH between 26 and 32 weeks
monitoring Hashimoto’s thyroiditis
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
postpartum dosage changes
- Reduce dosage to patient’s preconception dose after delivery
- Check TSH at 6 weeks postpartum
Postpartum thyroiditis
-definition and etiology
-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
classic picture of postpartum thyroiditis
- 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%
symptoms of thyrotoxic phase? why is it often missed?
- heat intolerance, nervousness, palpitations
- masked by stressors of being a new mom, not sleeping, returning to work, etc
monitoring postpartum thyroiditis
- 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
prevention of postpartum thyroiditis?
selenium was found to be effective in one trial
- significant decr in frequency of postpartum thyroid dysfunction
- decr TPOab levels during PG
