thyroid

1. Thyroid Disorder in
Pregnancy

2. Outline
Changes during pregnancy
• Hyperthyroidism
• Hypothyroidism
• Post partum thyroid disease
• Thyroid cancer
• Euthyroid with autoimmune thyroid disease

3. Iodine requirement in pregnancy
Iodine requirement increases in pregnancy
due to –
• Increase thyroid hormone production
• Increase renal excreation
• Increase demand of fetus

4. Iodine requirement
ATA 2017:
• 150 mcg/day during planing for pregnancy
• 220 mcg/day during pregnancy
• 290 mcg/day during lactation
• WHO –
• 250 mcg/day during pregnancy & lactation

5. Changes during pregnancy
Increase TBG –
• 2nd ary to increase estrogenic stimulation
& reduced hepatic clearance of TBG.
• TT3,TT4 increases.
• FT3, FT4 increase in 1st trimester in response
to elevated hCG

6. hCG –
• Intrinsic thyrotropic activity
• Begins shortly after gestation,
peaks at 10 wks, declines at 20
wks
• Activates thyroid receptor
• Transient decrease of TSH
during 8-11 wks due to peak in
hCG

8. Trimester specific TSH level
If trimester specific referance range is not
available in laboratory following referance
range is recommonded.
• 1st trimester : 0.1 – 2.5mIU/L
• 2nd trimester : 0.2 – 3.0 mIU/L
• 3rd trimester : 0.3 – 3.5 mIU/L

9. Who should test for TFT during pregnancy?
Targeted case finding vs universal screening?
• ATA, AACE, ACE recommend screening high risk case
only.
• However different studies have shown upto 30% cases
missed in high risk screening .
• In future universal screening of TFT should come in
action

10. High risk cases
• Previous H/O –Hyperthyroidism, Hypothyroidism, PPT, Thyroid lobectomy
• Positive family history
• Woman with goiter
• Positive thyroid antibodies
• S/S suggesting thyroid disorder
• Pt with T1DM ( as part of autoimmune polyendocrine syndrome)
• Other autoimmune disorder ( eg. Adisson disease, Vitiligo)
• Previous head neck irradiation
• H/O repeated abortions

11. Hyperthyroidism in pregnancy
• 0.2% of all pregnancies
• Causes are-
• Graves disease
• Toxic MNG, Toxic adenoma
• Sub Acute thyroiditis
• Gestational trophoblastic tumor
• Geststional Transient thyrotoxicosis
• Graves disease is most common ( 85%)

13. Graves disease
• Disease activity flactuates during
pregnancy .
• Exacerbation during 1st trimester with
gradual improvement during later
half.
• High risk of relapse during post
partum.

14. Gestational transient thyrotoxicosis
• Occurs in 1st trimester
• Due to hCG stimulates thyroid gland
• Thyroid gland usually not enlarged, no eye sign, no
prior history of thyroid disease, mild disorder &
associated emesis suggests transient thyrotoxicosis.
• Resolution of symptoms parallel to decline in hCG level
• Usually resolves spontaneously by 20 wks
• If persists beyond 20 wks, repeat evaluation for other
causes

15. Trophoblastic hyperthyroidism
• Associated with hydatidiform
mole & choriocarcinoma
• Nausea & vomiting predominant
• Unusual high hCG with snow
strom appearance on usg of L/A
are found

16. Diagnosis of hyperthyroidism
• TSH – Decreased
• FT4,FT3 – Increased
• TRAb – in GD ( when diagnostic uncertainity)
• Thyroid scan – contraindicated
• TT3, TT4 reference range should be adjusted at
1.5 times the non pregnant range

17. Treatment options of hyperthyroidism
• Anti thyroid drugs (ATD)
• Beta blockers( eg. propanolol for
2-6 wks)
• Thyroidectomy ( Rarely, If needed
done in 2nd trimester)

18. ATD
• ATD therapy should be uesd for hyperthyroism due to GD
in pregnancy.
• In 1st trimester –Propylthiouracil (PTU) – 100-
600mg/day
• 2nd & 3rd trimester – Carbimazole(CM) - 10-40mg/day
• Lowest possible dose to should be used.
• Pt education about possible ADR of drugs specially
teratogenecity
• PTU – Hepatoxicity
• Minor birth defects ( face & neck cysts)
• Urinary tract abnormalities( in male foetus)

19. Continued
Carbimazole –
• Teratogenicity -
• Apalasia cutis
• Choanal atresis
• Esophageal atresia
• For mother –
• Rash
• Agranulocytosis
• Both ATD & TRAb cross placenta
& can affect foetal thyroid

20. Monitoring
Clinical S/S of improvement:
• TSH, FT4/TT4 every 4 wkly.
• ATD dose has to be reduced when TSH is
in reference range to avoid fetal
overtreatment.

21. Hypothyroidism
• Untreated hypothyroidism is associated with
sub fertility, so uncommon in pregnency.
• However the causes may be –
• Iodine deficiency
• Hashimoto thyroiditis
• Prior radio iodine therapy
• Prior thyroid surgery

22. Sign
Symptom
• Untreated hypothyroidism is associated
with sub fertility, so uncommon in
pregnency.
• However the causes may be –
• Iodine deficiency
• Hashimoto thyroiditis
• Prior radio iodine therapy
• Prior thyroid surgery

24. Investigation
• Raised TSH
• FT4 – normal/ suppresed
• Anti TPO antibody

26. Subclinical Hypothyroism
• TSH > 2.5mU/L
• Normal FT4
• Increase risk of Abruptio placenta, preterm baby
• Indication of treatment
• TPO (+)ve with TSH > pregnancy specific referance
range
• TPO (+)VE with TSH >2.5mU/L & below the upper limit
of pregnancy specific referance range
• TPO (-)ve with TSH > 10mU/L
• TPO (-)ve with TSH > pregnancy specific referance
range & below 10.0mU/L

27. Treatment
• By Oral levothyroxin
• Levothyroxin should be administered as
2mcg/kg/day
• Usual starting dose 100mcg/day & then titrate.
• If already on T4 before pregnancy, on confirmation
of pregnancy increase dose by 30% ( 20-50mcg)
• Never give FeSO4 simultaneously with T4. Separate
time for drug ingestion by at least 2 hrs

28. Monitoring
• By TSH every 4 wk until mid
gestation, & at least once near 30
wks of gestation ( ATA 2017)
• Target TSH < 2.5mU/L
• Target FT4 – upper end of normal

29. Euthyroid & TPOab (+) ve
• 2 times risk of miscarriage
• No risk of neonatal hypothyroidism
• Risk of developing overt hypothyroidism as
pregnancy progress, so check TFT between
28-32 wks of gestation
• Increase risk of post partum thyroiditis (
check TFT at 3 month post partum)

30. Post-partum thyroid dysfunction
• Post-partum thyroiditis is the occurance of thyroid
dysfunction , excluding graves disease, in the 1st
postpartum year in woman who were euthyroid prior to
pregnancy. ( ATA 2017)
• Aetiology:
• Chronic autoimmune thyroiditis.
• Presentation: triphasic pattern
• Transient thyrotoxicosis ( 2-6 months)
• Transient hypothyroidism(3-12 months)
• Euthyroidism

31. continued
DD of PPT:
Graves disease that relapse in post patum
period
Lymphocytic hypophysitis( rare)
Investigation:
TPO (+)ve in 80% case
Thyroid scan to diferentiate from GD ( low
uptake in thyrotoxic phase of PPT, high
uptake in GD)

32. Management
• Beta blockers if thyrotoxic & symptomatic until TFT
normalize. ATD not necessary.
• Levothyroxine if TSH > 10mU/L
• TSH 2.5-10mU/L with symptoms
• Prognosis:
• 25% recurrence in future pregnancies
• 30% permanent hypothyroidism within 10 yrs