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Hypothyroidism in Pregnancy

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IG: Leong Tak Kei Overt hypothyroidism complicates up to 3 of 1,000 pregnancies Subclinical hypothyroidism is estimated to be 2-5 % (Canaris GH, 2000) In Macau ... – PowerPoint PPT presentation

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Title: Hypothyroidism in Pregnancy


1
Hypothyroidism in Pregnancy
  • IG Leong Tak Kei

2
Epidermiology
  • Overt hypothyroidism complicates up to 3 of 1,000
    pregnancies
  • Subclinical hypothyroidism is estimated to be 2-5
    (Canaris GH, 2000)
  • In Macau, around 2-3 (rough estimation)

3
Control of Thyroid Function
  • Hypothalamus releases TRH
  • Act on the pituitary gland to release TSH
  • TSH causes the thyroid gland to release the
    thyroid hormones (T3 and T4)
  • TRH and TSH concentrations are inversely related
    to T3 and T4 concentrations.
  • 99 circulating T3 and T4 is bound to TBG.
  • 1

Aboubakr Elnashar
free form Biologically Active
4
Clinical / Subclinical Hypothyroidism
  • Serum TSH level gt 3.0 mIU/l
  • Subclinical hypothyroidism ? elevated TSH with
    normal FT4, FT3.

Clinical Hypothyroidism Subclinical Hypothyroidism
TSH High (gt10) High (gt3 - lt10)
Free T4 Low Normal
Free T3 Normal or low Normal
5
Types of Hypothyroidism
  • Primary hypothyroidism
  • Secondary/tertiary hypothyroidism
  • Iatrogenic
  • Environmental

6
Primary Hypothyroidism
  • Developed Countries
  • Hashimotos thyroiditis Chronic thyroiditis
  • prone to develop postpartum thyroiditis
  • Worldwide
  • Iodine deficiency (Rare in Macau)
  • Other Causes
  • Subacute thyroiditis -gt not associated with
    goiter
  • Thyroidectomy, radioactive iodine treatment

7
Hashimotos Thyroiditis
  • An inflammatory disorder of thyroid glands
  • More common on those with other autoimmune
    diseases
  • Almost 100 associated with anti-TPO antibody.
    (Fitzpatrick Russell)
  • May cause transient hyperthyroidism
  • PE Goiter, rubbery consistency, moderate in
    size, mostly bilateral, painless.

8
Hashimotos Thyroiditis
  • T cells recognize the patients own thyroid
    antigens as foreign
  • ? cytotoxic to thyroid epithelial cells
  • ? stimulate B cells to make anti-thyroid
    antibodies, anti-peroxidase antibody,
    anti-thyroglobulin antibody, and
    anti-TSH-receptor antibody
  • ? block the action of TSH,
    leading to hypothyroidism!!

9
Hashimotos Thyroiditis
Lymphoid infiltrate, often with germinal centers
10
Iodine Deficiency
  • Affect 38 of worldwide population (Pearce EN,
    2008)
  • Sources Iodized salt and seafood. Others cow
    milk, egg, beans
  • Perinatal mortality
  • Congenital cretinism (growth failure, mental
    retardation, other neuropsychological deficits)

  • ACOG
  • Average intake 250 µg/d
  • Urine iodine gt 150 µg/d
  • Diana L.
    Fitzaptrick 2007

11
Subacute Thyroiditis
  • Subacute granulomatous thyroiditis
  • - Painful - Fever, myalgia
  • - Viral infection
  • Subacute lymphocytic thyroiditis
  • - includes postpartum thyroiditis
    (Prevalent 5 )
  • - Painless
  • Symptomatic Tx for initial hyperthyroidism

12
Subclinical Hypothyroidism
  • Elevated TSH (gt 3.0 mIU/l) with normal FT4, FT3.
  • 31 with anti-TPO antibody (Casey BM, 2007)
  • More common on women with autoimmune diseases
  • 50 ? hypothyroidism in 8 years
  • May cause childhood IQ decrease
  • Increase in preterm 4 vs 2.5 in euthyroid
    mother (Casey BM, 2007)

13
Secondary and Tertiary Hypothyroidism
  • lt1 hypothyroidism cases
  • Low or normal serum TSH concentrations low
    serum T4 and T3
  • 2nd (TSH deficiency) hypothyroidism
  • - pituitary tumor
  • - postpartum pituitary necrosis (Sheehan's
    syndrome)
  • - trauma, infiltrative diseases.
  • 3rd (TRH deficiency) hypothyroidism can be
    caused by
  • - Damages the hypothalamus or
  • - Interferes with hypothalamic-pituitary
    portal blood flow

14
Medication Cause
GIT Absorption of thyroid hormone. Separated by
4 hours
Inhibit
15
Symptoms of Hypothyroidism
  • Slowing of metabolic processes
  • Lethargy/fatigue weight gain
    cognitive dysfunction
  • cold intolerance constipation
    bradycardia
  • delayed relaxation of tendon reflexes
  • slow movement and slow speech
  • Deposition of matrix substances
  • Dry skin hoarseness
    edema
  • puffy face and eyebrow loss
    peri-orbital edema
  • enlargement of the tongue
  • Others
  • Decreased hearing myalgia and
    paresthesia depression
  • menorrhagia arthralgia
    pubertal delay
  • galactorrhea

16
Overlapping Complaints
Symptoms Hypothyroidism Pregnancy
Fatigue
Constipation
Hair Loss
Dry Skin
Brittle Nail
Weight Gain
Fluid Retention
Bradycardia
Carpel Tunnel Syndrome
17
Physiologic Changes in Pregnancy
  • Pregnancy is a state of relative iodine
    deficiency, because
  • - Active transport to fetoplacental unit
  • - Increase iodine excretion in urine, 2
  • fold
  • (increased GFT decreased renal tubular
    reabsorption)
  • - Thyroid gland increases its uptake
  • from the blood

18
  • TBG
  • - Increase (hepatic synthesis is
    increased)
  • TT4 TT3
  • - Increase to compensate for this rise
  • FT4 FT3 (crosses the placenta in the 1st half
    of pregnancy)
  • - Decrease. FT4 are altered less by
    pregnancy,
  • but do fall little in the 2nd 3rd
    trimesters.
  • TSH (does not cross placenta)
  • - decreases in 1st trimester, between 8 to
    14 wks
  • HCG, HCG has thyrotropin-like
    activity
  • - Increase in 2nd 3rd trimester
    (Increased TBG)

19
Changes of Hormones in Pregnancy
20
Screening and Its Importance
21
  • Overt hypothyroidism in pregnancy is rare
  • In continuing pregnancies hypothyroidism is
    associated with increased risk of
  • Pre-eclampsia
  • Placenta Abruption
  • increased c-section rates
  • Fetal death (especially if increased TSH occurs
    in 2nd trimester)

  • Motherisk April 2007

22
More for the Baby!!
  • Maternal thyroid hormones are important in
    embryogenesis
  • No production until 12 weeks, therefore needs
    moms T4 for fetal brain development
  • Maternal hypothyroidism can cause negative effect
    on fetal intellectual development.
  • Higher incidence of LBW (due to medically
    indicated preterm delivery, pre-eclampsia,
    abruption)
  • Iodine deficient hypothyroidism -gt congenital
    cretinism (growth failure, mental retardation,
    other neuropsychological deficits)




  • Motherisk April
    2007, CMAJ Apr 2007 176(8)

Treatment before 10 weeks gestation ? No adverse
effect
23
Indications for Screening universal
screening is not recommended (ACOG)
  • Family Hx of autoimmune thyroid disease
  • Women on thyroid therapy
  • Presence of goiter or thyroid nodules
  • Hx of thyroid surgery
  • Infertility
  • Unexplained anemia or hyponatremia or high
    cholesterol level
  • Previous Hx of
  • - neck radiation
  • - postpartum thyroid
    dysfunction
  • - previous birth of
    infant with thyroid
  • problem
  • Other autoimmune chronic conditions Type 1 DM

24
Laboratory Workup
  • Overt hypothyroidism
  • symptomatic patient
  • elevated TSH level
  • low levels of FT4 and FT3
  • Subclinical hypothyroidism
  • asymptomatic patient
  • elevated TSH
  • normal FT4 and FT3

25
Treatment
  • Replacement with external thyroid hormone --
    levothyroxine (Levothyroid, Levoxyl, Synthroid,
    and Unithroid).
  • Levothyroxine (Synthroid) pregnancy category A
  • A sterioisomer of physiologic thyroxine
  • 1.6 mcg/kg,
  • usually about 50 to 100 mcg/day for women
  • 30-60 minutes before
  • eating breakfast.

26
Treatment and Goals
  • The American Association of Clinical
    Endocrinologists recommends keeping the
    thyroid-stimulating hormone (TSH) level between
    0.3 and 3.0 mIU/L.
  • After readjustment of levothyroxine, observe 6-8
    weeks
  • Check TSH every trimester

27
Side Effects of Synthroid
  • Rapid or irregular heartbeat
  • Chest pain or shortness of breath
  • Muscle weakness
  • Nervousness
  • Irritability
  • Sleeplessness
  • Tremors
  • Change in appetite
  • Weight loss

28
Pearls
  • Safe in pregnancy and lactation
  • Very little thyroxin crosses the
    placenta
  • NO risk of thyrotoxicosis of fetus
  • Patients who were on thyroxine therapy before
    pregnancy should increase the dose by 30 once
    pregnancy is confirmed (Bombrys et al, 2008)
  • Keep TSH level between 0.3 and 3.0 mU/L.
  • TSH should be monitored every trimester until
    delivery.

29
THANK YOU
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