Hypothyroidism During Pregnancy

Introduction:

As soon as pregnancy is established normal physiology of women changes to great extend including hormone millicu. All these changes happen to accommodate fetus in maternal environment & adequate development of fetus. Thyroid hormone is one of major hormone changes occurs during pregnancy due to increase in placental hormone, body fluid content changes & also changes in protein component leading to changes in various hormone binding proteins.

There changes help in improved outcome of pregnancy & appropriate neurodevelopment of fetus. The functioning of thyroid gland is significantly altered by pregnancy.

The production of thyroxine (T4), Triiodothyronine (T3) increase almost one & half times in pregnancy.

In healthy women, these changes take place seamlessly, but many women with borderline thyroid status develop abnormalities in functioning of thyroid gland during pregnancy.

Thyroid dysfunction during pregnancy is widely prevalent & undetected hypothyroidism can adversely affect perinatal & fetal outcome. That is why, the assessment of thyroid function in pregnancy is of immense importance.   

Clinical features:

The symptoms of hypothyroidism during pregnancy & in non pregnant state are similar. This can range from fatigue, hair fall, dry skin, intolerance to cold, gain in weight constipation etc. Many of these symptoms occur commonly in pregnancy & identification of hypothyroidism on the basis of symptoms can be misleading. Pregnancy women with hypothyroidism often do not manifest any symptoms. Subclinical hypothyroidism (SCH) is usually asymptomatic & detected only on laboratory testing.

Laboratory finding:  

To meet the metabolic demands, during pregnancy, the thyroid physiology is altered. These changes are also reflected in alternation in thyroid function tests. The thyroxine binding  globulin (TBG) is elevated that in turn raises the total T4 & T3 level by 1.5 times higher than in non pregnancy state.

  • Raised TSH suggests –  Primary hypothyroidism
  • Serum free T4 levels distinguish between subclinical hypothyroidism & overt hypothyroidism depending on whether free T4 is normal as below normal for gestational age.
  • Thyroid  auto antibodies titers TPO-Ab & TG-Ab to confirm the auto immure  origin of the disorder.

Treatment :

  • Levothyoxine is treatment of choice
  • Women who already take thyoxine before pregnancy usually need to increase their daily dosage by 30% – 50% above preconception dose. The thyroxine dose usually need to be incremented by 4-6 weeks of gestation.

Post natal

  • After delivery, reduce the levothyroxine dose after 4 weeks.
  • Women with evidence of thyroid autoimmunity are at risk of developing post partum thyroiditis. Therefore continue monitoring thyroid profile for at least 6 months after delivery is necessary.

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