Transcript Hypothyroidism in Pregnancy - Home

IG: Leong Tak Kei
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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)
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%
free form Biologically
Active
Aboubakr Elnashar
• Serum TSH level > 3.0 mIU/l
• Subclinical hypothyroidism  elevated TSH with
normal FT4, FT3.
Clinical
Hypothyroidism
Subclinical
Hypothyroidism
High (>10)
High (>3 - <10)
Low
Normal
Normal or low
Normal
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Primary hypothyroidism
Secondary/tertiary hypothyroidism
Iatrogenic
Environmental
Developed Countries
 Hashimoto’s thyroiditis – Chronic thyroiditis
prone to develop postpartum thyroiditis
Worldwide
 Iodine deficiency (Rare in Macau)
Other Causes:
◦ Subacute thyroiditis -> not associated with goiter
◦ Thyroidectomy, radioactive iodine treatment
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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.
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T cells recognize the patient’s own thyroid
antigens as foreign
 cytotoxic to thyroid epithelial cells
 stimulate B cells to make anti-thyroid
antibodies, anti-peroxidase antibody, antithyroglobulin antibody, and anti-TSHreceptor antibody
 block the action of TSH, leading to
hypothyroidism!!
Lymphoid infiltrate,
often with germinal
centers
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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
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Average intake 250 µg/d
Urine iodine > 150 µg/d
Diana L. Fitzaptrick 2007
Subacute granulomatous thyroiditis
- Painful - Fever, myalgia
- Viral infection
 Subacute lymphocytic thyroiditis
- includes postpartum thyroiditis (Prevalent:
5% )
- Painless
Symptomatic Tx for initial hyperthyroidism
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Elevated TSH (> 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)
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<1% hypothyroidism cases
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Low or normal serum TSH concentrations + low serum T4 and
T3
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2nd (TSH deficiency) hypothyroidism:
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- 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
Ferrous Sulfate
Sucralfate
Inhibit
Cholestyramine
Aluminium
Hydroxide
GIT
Absorption
of thyroid
hormone.
Separated
by 4 hours
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Slowing of metabolic processes:
Lethargy/fatigue
weight gain
cold intolerance
constipation
delayed relaxation of tendon reflexes
slow movement and slow speech
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Deposition of matrix substances:
Dry skin
hoarseness
puffy face and eyebrow loss
enlargement of the tongue
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cognitive dysfunction
bradycardia
edema
peri-orbital edema
Others
Decreased hearing
menorrhagia
galactorrhea
myalgia and paresthesia
arthralgia
depression
pubertal delay
Symptoms
Fatigue
Constipation
Hair Loss
Dry Skin
Brittle Nail
Weight Gain
Fluid Retention
Bradycardia
Carpel Tunnel
Syndrome
Hypothyroidism
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
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)
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Overt hypothyroidism in pregnancy is rare
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In continuing pregnancies hypothyroidism is
associated with increased risk of:
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Pre-eclampsia
Placenta Abruption
increased c-section rates
Fetal death (especially if increased TSH occurs in
2nd trimester)
Motherisk April 2007
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Maternal thyroid hormones are important in embryogenesis
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No production until 12 weeks, therefore needs mom’s T4 for
fetal brain development
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Maternal hypothyroidism can cause negative effect on fetal
intellectual development.
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Higher incidence of LBW (due to medically indicated preterm
delivery, pre-eclampsia, abruption)
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Iodine deficient hypothyroidism -> 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
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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
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Overt hypothyroidism:
symptomatic patient
elevated TSH level
low levels of FT4 and FT3
Subclinical hypothyroidism:
asymptomatic patient
elevated TSH
normal FT4 and FT3
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Replacement with external thyroid hormone
-- levothyroxine (Levothyroid, Levoxyl,
Synthroid, and Unithroid).
Levothyroxine (Synthroid)
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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.
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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
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Rapid or irregular heartbeat
Chest pain or shortness of breath
Muscle weakness
Nervousness
Irritability
Sleeplessness
Tremors
Change in appetite
Weight loss
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Safe in pregnancy and lactation
Very little thyroxin crosses the placenta
NO risk of thyrotoxicosis of fetus
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Patients who were on thyroxine therapy before
pregnancy should increase the dose by 30% once
pregnancy is confirmed (Bombrys et al, 2008)
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Keep TSH level between 0.3 and 3.0 mU/L.
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TSH should be monitored every trimester until
delivery.