Thyroid in pregnancy Dr Ash Gargya Endocrinologist, RPA and Bankstown Hospitals VMO, Norwest and...
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Transcript of Thyroid in pregnancy Dr Ash Gargya Endocrinologist, RPA and Bankstown Hospitals VMO, Norwest and...
![Page 1: Thyroid in pregnancy Dr Ash Gargya Endocrinologist, RPA and Bankstown Hospitals VMO, Norwest and Strathfield Private Hospitals.](https://reader036.fdocuments.net/reader036/viewer/2022081414/55143c4e550346284e8b46e4/html5/thumbnails/1.jpg)
Thyroid in pregnancy
Dr Ash Gargya
Endocrinologist, RPA and Bankstown Hospitals
VMO, Norwest and Strathfield Private Hospitals
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Maternal physiology and TSH recommendations
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Changes in maternal thyroid physiology
• E2 ↑ TBG synthesis (2-fold) and sialylation → ↓ TBG plasma clearance → ↑ in total T4 (and T4 binding sites) and T3
• ↑ volume of distribution and placental T4 transfer (accounts for 35% cord T4)
• hCG has TSH-like activity → peak 10-12 wks → 1st trimester ↑ fT4 (i.e. thyroid hormone pool) and ↓ TSH (~20% pregnancies)
• ↑GFR → ↑ (2-fold) urinary iodine loss
0 10 20 30 40 Gestation (wks)
“Strains” the thyroid functional reserve esp if ATA +ve or iodine insufficient
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What crosses the placenta?
T4 • TSH and T3 do not cross the placenta
IodineAnti-thyroid medications
• PTU and carbimazole
TSH receptor antibodies• A maternal level >3 times ULN in the
third trimester may increase the risk of neonatal Graves’
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TSH reference ranges in pregnancy
Glinoer D. Nat Rev Endo 2010
9 studies between 2004-2009ATA –ve and iodine sufficientNon-pregnant TSH reference range (0.4-4.1)mIU/L
97.5th centile
2.5th centile
Mean
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Current recommendations
Where available, use laboratory-specific and trimester-specific reference ranges in pregnancy
When not available, aim for:-
Pre-conception TSH 0.3-2.5mIU/L
1st trimester TSH 0.1-2.5mIU/L
2nd trimester TSH 0.3-3.0mIU/L
3rd trimester TSH 0.3-3.0mIU/L
ATA Guidelines July 2011
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Current recommendations
fT4 less reliable in pregnancy• Depends on methodology (ED and MS gold
standard)• Effect of iodine insufficiency
When is fT4 measurement useful?• Differentiate OH from SH • Monitoring anti-thyroid therapy
o Aim fT4 upper non-pregnant RR (i.e. 15-20pmol/L)
• Central hypothyroidism
ALL pregnant and breastfeeding women should be on an iodine-containing (250mcg) supplement
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Who should be screened pre-conception?
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Universal screening is currently NOT advocated
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Maternal hypothyroidism
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What are the implications of maternal hypothyroidism?
OVERT hypothyroidism (OH)
• Definition: TSH >2.5 with low fT4
• TSH >10 regardless of fT4
• Obstetric: associated with miscarriage, SGA, prematurity, gestational hypertension and PPH
• Fetal: 7 point IQ deficit (age 7-9yo) with delays in language, attention and motor development [untreated maternal TSH>13] (Haddow 1999)
• T4 therapy IMPROVES outcomes (obstetric and fetal)
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What are the implications of maternal hypothyroidism?
SUBCLINICAL hypothyroidism (SH)
• Affects 2-3% of all pregnancies
• Definition: TSH 2.5-10 with normal fT4
• Obstetric: associated with increase risk of miscarriage and pre-term delivery (OR 2-2.5 across multiple studies)
• Fetal: no convincing evidence that SH affects neuro-cognitive development
• SCARCE evidence confirming that T4 intervention improves outcomes (obstetric or fetal)
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Adjusting and monitoring TFT on Thyroxine
For women with pre-existing hypothyroidism on Thyroxine
• Aim TSH 0.3-2.5 pre-conception
• Once pregnant, increase dose by 30% (usually = 2 extra tablets through the week)
• For athyreotic women a dose increase up to 50% is needed
• Monitor TFT 4-weekly till 20 weeks and once at 28-32 weeks
• Take prenatal/Ca/Fe supplements >3h gap from Thyroxine
• Post-delivery reduce to pre-pregnancy dose with 3-monthly monitring for 1 year• Hashimoto’s: dose may be 20% higher 1 year postpartum cf pre-
preg
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What are the implications of positive thyroid autoimmunity?
Occurs in 5-15% of child-bearing women
Positive thyroid antibodies are associated with• SH and OH
• Postpartum thyroiditis (risk 30-50% if +ve in 1st trimester)
• Increased rate of miscarriage (OR 2.73)o ?Heightened immune dysregulation
o ?Thyroid hypofunction
o ?Increased maternal age
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What are the implications of positive thyroid autoimmunity?
Guidelines recommend treating with T4 if• Euthyroid and history of recurrent miscarriage
• SH
If euthyroid with +ve ATA pre-conception
• 20% of these women will have a TSH>4 by the 3rd trimester
• Monitor 4-6 weekly till mid-gestation (and once at 28-32 weeks) for SH/OH
• Monitor TFT 3-monthly pp - increased risk of pp thyroiditis
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ATA guidelines 2011
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Maternal hyperthyroidism
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What are the implications of maternal hyperthyroidism?
Affects 0.1-0.4% of pregnancies
85% have Graves’ disease
• Other causes include hCG-mediated thyrotoxicosis (hyperemesis gravidarum, twin pregnancy), toxic nodule/s, thyroiditis (subacute, postpartum – M/C or delivery <12 months), molar pregnancy
Overt hyperthyroidism associated with miscarriage, IUGR, pre-eclampsia, preterm delivery, thyroid storm, CCF
Subclinical hyperthyroidism is NOT associated with adverse feto-maternal outcomes
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How to approach a low TSH in early pregnancy
Check fT4, TRAb
• If both elevated – treat with antithyroid meds
• fT3 may help confirm Graves’ - T3 toxicosis (DD AFTN)
• If normal fT4 and +ve TRAb – monitor TFT 4-weekly and treat once overtly hyperthyroid
• If normal fT4 and –ve TRAb, likely hCG-mediated thyrotoxicosis
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Graves’ disease in pregnancy
Use lowest effective dose of ATD
PTU in the 1st trimester (monitor LFT) and carbimazole thereafter if continued therapy required
Maintain fT4 in the upper 1/3 of non-pregnant RR
Monitor TFT 4-weekly whilst on ATD
Check TRAb around 28-32 weeks – risk neonatal Graves’
1/3 women can stop ATD by 3rd trimester
High risk of relapse 4-8 months postpartum
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Summary
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Summary
Use laboratory-specific, trimester-specific RR in pregnancy
TSH 0.3-2.5 pre-conception and during the 1st trimester
TSH 0.3-3.0 during the 2nd and 3rd trimesters
If on Thyroxine, increase dose by 30-50% once pregnant with 4-weekly monitoring in the first half of pregnancy
ALL women should take an iodine–containing supplement
Maintain fT4 in upper 1/3 non-preg RR if on ATD