Hyperthyroidism During pregnancy

Hyperthyroidism
During pregnancy
Prof. Aboubakr Elnashar
BenhaUniversity Hospital

Physiological changes of thyroid during
pregnancy
1. TBG
Increase {hepatic synthesis is increased}
2.TT4 &TT3
Increase to compensate for this rise
ABOUBAKRELNASHAR

3. FT4 & FT3
Decrease.
FT4 are altered less by pregnancy, but do fall a little in
the 2nd & 3rd trimesters.
4.TSH
Decrease in 1st trimester, between 8 & 14 ws
{increase HCG, HCG has thyrotropin-like activity},
Increase in 2nd & 3rd trimester {IncreasedTBG}
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Non-pregnant 1st trimester 2nd trimester 3rd trimester
TSH mu/l 0-4 0-1.6 0.1-1.8 0.7-7.3
FT4 pmol/l 11-23 11-22 11-19 7-15
FT3 pmol/l 4-9 4-8 4-7 3-5
The shaded area
represents the
normal range in
non pregnant
ABOUBAKRELNASHAR

To screen or not to screen?
1.Infertility
2.Menstrual disorders
3.Repeated pregnancy loss (RCOG do not recommend)
4.TIDM
5.Pregnant women:
ABOUBAKRELNASHAR

5. Pregnant women:
a. Routine:
Some authors recommend screening all pregnant women
(Mitchell ML, Klein , 2004)
Routine screening is not (ACOG, 2002)
b.Selective: (Mestman, 2004)
. S and S of the disorder, goiter
. Family history of autoimmune thyroid disease
.TIDM.
. History of high-dose neck radiation, thyroid therapy,
postpartum thyroiditis, or an infant born with thyroid
disease
ABOUBAKRELNASHAR

Incidence
•Women>men (10:1).
•1 in 500 pregnancies.
•50%: family history of autoimmune thyroid disease.
•Most cases encountered in pregnancy have already
been diagnosed and will already be on treatment.
•If thyrotoxicosis occurs for the first time in
pregnancy, it usually presents late in 1st or early in
2nd trimester.
ABOUBAKRELNASHAR

Clinical features
•Many features are common in normal
pregnancy:
heat intolerance, tachycardia,
palpitations, palmar erythema,
emotional lability, vomiting and
goitre.
•Discriminatory features:
weight loss
tremor,
persistent tachycardia
lid lag, exophthalmosABOUBAKRELNASHAR

Eye signs
•50%
•{thyroid disease at some
time rather than active
thyrotoxicosis, may occur
before hyperthyroidism}
ABOUBAKRELNASHAR

Pathogenesis
•95%: Graves' disease.
(autoimmune disorder caused by TSH receptor-stimulating antibodies).
These autoantibodies cross the placenta and can cause fetal and neonatal
thyroid dysfunction even when the mother herself is in a euthyroid condition.
•More rarely:
Toxic multi-nodular goitre
Toxic adenoma,
Subacute thyroiditis
Iodine, amiodarone or lithium therapy.
Choriocarcinoma
Molar pregnancyABOUBAKRELNASHAR

Antibodies Type Associated with
Antithyroid Thyroglobulin
Thyroid peroxidase
(anti-TPO)
Postpartum thyroiditis
Fetal & neonatal
hyperthyroidism
TSH-receptor Thyroid-stimulating
immunoglobulin
(TSI)
Graves’ disease
TSH-receptor
antibody
Fetal goiter
Congenital hypothyroidism
Chronic thyroiditis without
goiter
ABOUBAKRELNASHAR

Screening for maternal thyroid antibodies:
1. Graves’ disease with fetal or neonatal
hyperthyroidism in a previous pregnancy
2. Active Graves’ disease being treated with
antithyroid drugs
3. Euthyroid or have undergone ablative therapy and
have fetal tachycardia or IUGR
4. Chronic thyroiditis without goiter
5. Fetal goiter on ultrasound.
Screening for neonatal thyroid antibodies:
congenital hypothyroidism
ABOUBAKRELNASHAR

Diagnosis
•Overt:
Raised FT4 or FT3, decreased TSH
•Subclinical:
Decreased TSH, normal FT4 and FT3
•D.D from hyperemesis gravidarum may be
difficult.
TSH FT4 FT3 TT4 TT3
No change No change ↑ ↑ ↑ Pregnancy
↓ ↑ ↑ ↑ ↑ Hyperthyroidism
↓ No change No change No change No
change
Subclinical
hyperthyroidism
ABOUBAKRELNASHAR

Effect of pregnancy on thyrotoxicosis
1. Exacerbations may occur in:
1st trimester {hCG production}
puerperium {reversal of the fall in antibody levels seen
during pregnancy}.
2. Improvement and a lower requirement for
antithyroid treatment during 2nd and 3rd
trimesters.
{As with other autoimmune conditions, there is a state
of relative immunosuppression in pregnancy and
levels of TSH receptor-stimulating antibodies may fall}
3. Pregnancy has no effect an Graves' ophthalmapathy.
ABOUBAKRELNASHAR

Effect of thyrotoxicosis on pregnancy
•If thyrotoxicosis is severe and untreated: inhibition
of ovulatian and infertility.
•For those with good control on antithyroid drugs or
with previously treated Graves' disease in
remission, the maternal and fetal outcome is usually
good and unaffected by the thyrotoxicosis.
1. Untreated have an increased rate of miscarriage,
IUGR, PTL and perinatal mortality, congestive
heart failure, PET.
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2. Poorly controlled: thyroid crisis ('storm') and heart
failure, particularly at the time of delivery.
3. Rarely retrosternal extension of a goitre may
cause tracheal obstruction. This is a particular
problem if the patient needs to be intubated.
4. Thyroid stimulating antibodies may cause fetal or
neonatal thyrotoxicosis
ABOUBAKRELNASHAR

Thyroid storm
Rare: 1% to 2% of patients receiving thioamide therapy.
In most instances: a complication of uncontrolled hyperthyroidism,
Precipitated by: infection, surgery, thromboembolism, PET, labor, and delivery.
Potentially lethal
C.P:
Fever, nausea, vomiting, diarrhea, tachycardia, altered mental status,
restlessness, nervousness, seizures, coma, and cardiac arrhythmias.
ABOUBAKRELNASHAR

Treatment:
Should be initiated before the results of TSH, FT4, and FT3 tests are available.
Delivery should be avoided, if possible, until the mother’s condition
can be stabilized but, if the status of the fetus is compromised,
delivery is indicated.
Begin with stabilization of the patient, followed by initiation of a
stepwise management approach
ABOUBAKRELNASHAR

Management
Antithyroid drugs
Mechanism of action:
PTU:
Blocks the oxidation of iodine in the thyroid gland: prevent
synthesis of T4 and T3.
Methimazole:
blocks the organification of iodide: decreases thyroid
hormone production.
ABOUBAKRELNASHAR

Dose: Initial (4-6 w) Maintenance (12-
18 m)
Carbimazole: 15-40 mg 5-15 mg
PTU: 150-400 mg 50-150 mg
Relapse rates are high, and some women are managed with
long-term antithyroid drugs.
ABOUBAKRELNASHAR

•The aim of treatment:
1. Control the thyrotoxicosis as rapidly as possible
2. Maintain optimal control 'with the lowest dose
of antithyroid medication.
•Monitoring:
-The woman should be clinically euthyroid,
-F T4 at the upper end of the normal range.
=Thyroid function: /4 w (until TSH and FT4 are
within normal) /trimester thereafter.
ABOUBAKRELNASHAR

•Side effects:
1. Maternal:
a. Drug rash or urticaria (1-5%)
b. More rarely carb may cause neutropenia and
agranulocytosis.
Women should be asked to report any signs of
infection (sore throat)
CBC, if there is clinical evidence of infection
Carb should be stopped immediately if there is
any clinical or laboratory evidence of
neutropenia.ABOUBAKRELNASHAR

2. Foetal:
a. High doses may cause fetal hypothyroidism and
goitre {Both drugs cross the placenta, PTU< carb}
There is no place for 'block-and-replace' regimens.
Thyroxine 'replacement' does not cross the
placenta in sufficiently high doses to protect the
fetus.
b. Neither is grossly teratogenic, although carbim
occasionally causes a scalp defect (aplasia cutis).
•Doses of PTU at or below 150 mg/day and carb 15
mg/day are unlikely to cause problems in the fetus.
ABOUBAKRELNASHAR

3. During lactation:
•Very little PTU (0.07%) and carb (0.5%) is excreted
in breast milk): safe for mothers to breast-feed while
taking doses of PTU at or below 150 mg/day and carb
15 mg/day
•High doses of antithyroid drugs: Thyroid function
should be checked in umbilical cord blood and at
regular intervals in the neonate
•PTU is preferable for newly diagnosed cases in pregnancy
{less transfer across the placenta and to breast milk}, but
women already on maintenance carb prior to pregnancy
need not be switched to PTU in pregnancy.
ABOUBAKRELNASHAR

B Blockers
•Indications:
1. In the early management of thyrotoxicosis
2. During relapse to improve sympathetic
symptoms of tachycardia, sweating and
tremor.
•They are discontinued once there is clinical
improvement, usually evident within 3 ws.
•Doses: 40 mg tds for such short periods of time
are not harmful to the fetus.
ABOUBAKRELNASHAR

Surgery (Thyroidectomy)
Indications: Rarely
1. Dysphagia or stridor related to a large goitre.
2. Confirmed or suspected carcinoma.
3. Allergies to both antithyroid drugs.
Best performed in: 2nd trimester.
Complications:
1. Hypothyroidism (25-50%)
close follow-up to ensure rapid diagnosis and
treatment with replacement therapy.
2. Hypocalcaemia
{removal of the parathyroid glands}ABOUBAKRELNASHAR

Radioactive iodine
Contraindicated:
1. Pregnancy
2. Breast-feeding {it is taken up by the fetal thyroid (after
10-12 weeks) with resulting thyroid ablation and
hypothyroidism}.
•Pregnancy should be avoided for at least 4 months after
treatment {risk of chromosomal damage and genetic
abnormalities}.
Diagnostic radioiodine scans (as opposed to treatment)
contraindicated in pregnancy
may be performed if a mother is breast-feeding, although
mothers should stop breast-feeding for 24 hrs after the
procedure. ABOUBAKRELNASHAR

BenhaUniversity Hospital, Egypt
E-mail:elnashar53@hotmail.comABOUBAKRELNASHAR

Hyperthyroidism During pregnancy

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Hyperthyroidism During pregnancy