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Thyroid in pregnancy Dr Ash Gargya Endocrinologist, RPA and Bankstown Hospitals VMO, Norwest and Strathfield Private Hospitals.

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Presentation on theme: "Thyroid in pregnancy Dr Ash Gargya Endocrinologist, RPA and Bankstown Hospitals VMO, Norwest and Strathfield Private Hospitals."— Presentation transcript:

1 Thyroid in pregnancy Dr Ash Gargya Endocrinologist, RPA and Bankstown Hospitals VMO, Norwest and Strathfield Private Hospitals

2 Maternal physiology and TSH recommendations

3 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 wks 1 st trimester fT4 (i.e. thyroid hormone pool) and TSH (~20% pregnancies) GFR (2-fold) urinary iodine loss Gestation (wks) Strains the thyroid functional reserve esp if ATA +ve or iodine insufficient

4 What crosses the placenta? T4 TSH and T3 do not cross the placenta Iodine Anti-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

5 TSH reference ranges in pregnancy Glinoer D. Nat Rev Endo studies between ATA –ve and iodine sufficient Non-pregnant TSH reference range ( )mIU/L 97.5 th centile 2.5 th centile Mean

6 Current recommendations Where available, use laboratory-specific and trimester- specific reference ranges in pregnancy When not available, aim for:- Pre-conception TSH mIU/L 1 st trimesterTSH mIU/L 2 nd trimesterTSH mIU/L 3 rd trimesterTSH mIU/L ATA Guidelines July 2011

7 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 pmol/L) Central hypothyroidism ALL pregnant and breastfeeding women should be on an iodine- containing (250mcg) supplement

8 Who should be screened pre-conception?

9 Universal screening is currently NOT advocated

10 Maternal hypothyroidism

11 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)

12 What are the implications of maternal hypothyroidism? SUBCLINICAL hypothyroidism (SH) Affects 2-3% of all pregnancies Definition: TSH with normal fT4 Obstetric: associated with increase risk of miscarriage and pre-term delivery (OR across multiple studies) Fetal: no convincing evidence that SH affects neuro-cognitive development SCARCE evidence confirming that T4 intervention improves outcomes (obstetric or fetal)

13 Adjusting and monitoring TFT on Thyroxine For women with pre-existing hypothyroidism on Thyroxine Aim TSH 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 weeks Take prenatal/Ca/Fe supplements >3h gap from Thyroxine Post-delivery reduce to pre-pregnancy dose with 3-monthly monitring for 1 year Hashimotos: dose may be 20% higher 1 year postpartum cf pre-preg

14 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 1 st trimester) Increased rate of miscarriage (OR 2.73) o ?Heightened immune dysregulation o ?Thyroid hypofunction o ?Increased maternal age

15 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 weeks) for SH/OH Monitor TFT 3-monthly pp - increased risk of pp thyroiditis

16 ATA guidelines 2011

17 Maternal hyperthyroidism

18 What are the implications of maternal hyperthyroidism? Affects % 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

19 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

20 Graves disease in pregnancy Use lowest effective dose of ATD PTU in the 1 st 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 weeks – risk neonatal Graves 1/3 women can stop ATD by 3 rd trimester High risk of relapse 4-8 months postpartum

21 Summary

22 Use laboratory-specific, trimester-specific RR in pregnancy TSH pre-conception and during the 1 st trimester TSH during the 2 nd and 3 rd 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

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