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Thyroid disorders and pregnancy

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... last 6-9 months Postpartum depression Screen with a TSH as may be cause Treatment Hyperthyroid phase Anti-thyroid medications not effective Beta blockers for ... – PowerPoint PPT presentation

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Title: Thyroid disorders and pregnancy


1
Thyroid disorders and pregnancy
  • Medical Complications
  • November 23, 2007
  • Jill Newstead-Angel, MD FRCPC

2
Objectives
  • Discuss the normal physiology of the thyroid
    gland during pregnancy
  • Discuss hyperthyroidism and pregnancy
  • Diagnosis
  • Treatment
  • Discuss hypothyroidism and pregnancy
  • Diagnosis
  • Treatment
  • Discuss thyroid nodules in pregnancy

3
Case 1
  • 24 yr old G2P1 presents at 9 weeks GA for first
    prenatal visit
  • Part of screening blood work was TSH
  • TSH 0.5 mU/L
  • Clinically and on history - no evidence of
    thyroid disease

4
What should be done?
  • Book the patient for a radioactive iodine uptake
    scan
  • Start PTU at 100 mg bid
  • Do nothing at all
  • Check FT4 and FT3

5
Normal thyroid physiology in pregnancy
  • Fetal thyroid and fetal hypothalamic-pituitary-thy
    roid axis develop independently of maternal
    thyroid
  • Starts to function after 10 weeks GA
  • 11-12 weeks GA, fetal thyroid concentrates
    iodine and FT4 and TSH are present in fetal
    circulation

6
  • Increase in thyroid binding globulin due to
    increase in estrogen (stimulation of hepatic
    production and decreased degradation)
  • Increase in total T4 and T3
  • Increase in GFR leads to increase in renal iodine
    clearance

7
  • HCG has similar properties to TSH therefore has
    intrinsic thyroid stimulating activity
  • increase FT4 and FT3 levels during first
    trimester

8
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9
Increase frequency in goiters?
  • In iodine replete areas there is not an increased
    frequency of goiters during pregnancy
  • If there is a palpable goiter - should be further
    investigated as underlying thyroid disease is
    present 50 of the time

10
Hyperemesis Gravidarum
  • High levels of HCG
  • Associated biochemical evidence of
    hyperthyroidism
  • Does not need treatment
  • Follow patients out of first trimester to ensure
    not true hyperthyroidism

11
What should be done?
  • Book the patient for a radioactive iodine uptake
    scan
  • Start PTU at 100 mg bid
  • Do nothing at all
  • Check FT4 and FT3

12
Case 2
  • 33 year old G5P4 presents at 13 weeks GA for
    first prenatal
  • Complaining of palpitations, heat intolerance,
    and tremors
  • Clinically tachycardia, tremor and palpable
    thyroid with bruit

13
  • TSH lt0.01
  • FT4 33
  • FT3 9

14
Hyperthyroidism and pregnancy
  • Prevalence 0.1 to 0.4
  • Graves is the most common cause
  • Other causes
  • Functioning adenoma
  • Toxic mutlinodular goiter
  • Thyroiditis
  • Excessive thyroid hormone intake
  • Gestational transient thyrotoxicosis

15
  • Diagnosis difficult in pregnancy because of the
    hyper dynamic state of pregnancy
  • Eye signs, tremor, weight loss, marked
    tachycardia more suggestive of hyperthyroidism
  • Laboratory
  • low TSH with elevated FT4 and FT3
  • TSH receptor antibodies
  • TPO and TBG antibodies

16
Pregnancy outcome
  • Depends on treatment and control
  • Worse pregnancy outcomes with no treatment or
    partial treatment
  • Preterm labor
  • Preeclampsia
  • Stillbirth
  • Small for gestational age

17
Treatment
  • Antithyroid medications
  • PTU
  • partially inhibits the conversion of T4 to T3
  • Crosses the placenta less
  • Dose 100 600 mg
  • Methimazole
  • Aplasia cutis
  • Dose 10 40 mg
  • Transient leukopenia develops 10 women treated
  • Beta blockers
  • Propranolol - may be useful in those with marked
    tachycardia

18
  • Surgery
  • Second trimester best
  • Reserved for those that fail medical treatment
  • Radioactive iodine treatment
  • Contraindicated in pregnancy
  • Over all goal
  • treat maternal disease while limiting potential
    for fetal hypothyroidism

19
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20
Back to case
  • Send off blood work for Thyroid stimulating
    antibodies
  • Start PTU 100 mg tid
  • Start propanolol 10 - 20 mg bid
  • Repeat TSH in 2 weeks
  • Titrate medications to keep FT4 within higher
    limits of normal

21
Sub-clinical hyperthyroidism
  • Low TSH with normal FT4
  • Affects 1.7 of pregnant women
  • During pregnancy not found to be associated
    with any adverse outcomes

22
Case 3
  • 25 year old G1P1 seen preconception for
    hypothyroidism
  • Would like to conceive in the near future
  • Currently on Synthyroid 75 mcg per day
  • Most recent TSH 4 with normal FT4 and FT3

23
Hypothyroidism and pregnancy
  • 95 the result of primary disease of the thyroid
  • Autoimmune (Hashimotos thyroiditis)
  • Less common causes
  • Over treatment of hyperthyroidism
  • Transient hypothyroidism due to postpartum
    thyroiditis
  • Medications
  • Pituitary or hypothalamic disease

24
Diagnosis
  • 20-30 of patients have symptoms
  • Elevated TSH
  • Patients with central hypothyroidism do not
    manifest elevated TSH during pregnancy

25
Complications
  • Overt hypothyroidism
  • Gestational hypertension (36 of patients
  • Placental abruption
  • Spontaneous abortion
  • Preterm birth
  • Postpartum hemorrhage

26
  • Association between maternal hypothyroidism and
    impaired cognitive function of the offspring

27
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28
Thyroid replacement and medications
  • Drugs that interfere with absorption
  • Prenatal vitamins
  • Iron replacement
  • Antacids
  • Cholestyramine
  • Drugs that interfere with metabolism
  • Phenytoin
  • Rifampin
  • Carbamazapine

29
Back to case
  • Increase her medication to 100 mcg per day to get
    her TSH lt2.5 before conception
  • Once she becomes pregnant, check her TSH and
    adjust the dose as necessary
  • Monitor q trimester during pregnancy

30
Sub clinical hypothyroidism
  • Elevated TSH with normal FT4 and FT3
  • Prevalence 4-8.5
  • Pregnant women 2-5
  • Normal TSH 0.3 and 2.5 mU/L
  • Levels between 2.5 and 4.0 gray zone
  • Values gt4.0 indicative of early thyroid failure
  • Treat?
  • controversial

31
Postpartum Thyroiditis
  • Occurs in 5-10 of women
  • 25 of patients with DMI

32
  • Occurs 6-12 weeks postpartum
  • Phases
  • Hyperthyroid - last 1-2 months
  • Hypothyroid - last 6-9 months
  • Postpartum depression
  • Screen with a TSH as may be cause

33
Treatment
  • Hyperthyroid phase
  • Anti-thyroid medications not effective
  • Beta blockers for symptoms
  • Hypothyroid phase
  • Treat with replacement for 6-12 months and then
    reduce or discontinue dose and recheck TSH in 6
    weeks

34
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35
Thyroid nodules and cancer during pregnancy
  • Increase in the prevalence of thyroid nodule
    during pregnancy
  • Increase in the growth of existing nodules during
    pregnancy
  • No evidence to suggest thyroid cancer arises de
    novo more frequently during pregnancy

36
Evaluation
  • Lab evaluation of thyroid function
  • Ultrasound
  • FNA
  • Benign cytology - observe and follow postpartum
  • Malignant cytology - surgery recommended

37
  • Women with previously diagnosed or treated
    differentiated thyroid cancer require an increase
    in levothyroxine dosage during pregnancy
  • TSH of 0.1-0.8 mU/L for papillary or follicular
    cancer
  • TSH of lt2.5 mU/L for patients with medullary
    thyroid cancer

38
Summary
  • Normal physiology of pregnancy is such that the
    TSH will decrease in the first trimester due to
    similarities to HCG
  • If initially low, repeat second trimester and
    check FT4 and FT3
  • Hyperthyroidism - treat to maintain FT4 in the
    higher range of normal
  • Hypothyroidism - goal TSH 0.5 to 2.5 mU/L

39
  • Postpartum depression - screen for postpartum
    thyroiditis

40
Reference
  • Casey B, Leveno K. Thyroid disease in pregnancy.
    Obstetrics and Gynecology 2006 108 (5)
    1283-1292
  • Hypothyroidism in the pregnant woman. Drug and
    therapeutic bulletin 2005 44 (7) 53-55
  • LeBeau S, Mandel S. Thyroid disorders during
    pregnancy. Endocrinology and Metabolism Clinics
    of North America. 2006 35 117-136
  • Molitch M. Endocrine disease in pregnancy.
    Principles and Practice of Endocrinology and
    Metabolism 3rd edition.
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