Thyroid disorders in Pregancy

 Thyroid disease in pregnancy is very common and is the second most common endocrine disorder of women during reproductive age. Pregnancy leads to an increase in size of thyroid gland from 10-40% depending on iodine content of the area. Iodine requirement also increases by 50% with almost 50% increase in production of thyroxine (T4) and triiodothyronine (T3).

 

American Thyroid Association (ATA) first published its guidelines in 2011 but, significant scientific and clinical advances since then led ATA to revise the guidelines.

There was 162 pages of evidence based guidelines were first published online on January 06, 2017 in Thyroid. The 97 recommendations presented deals with nutrient requirements, screening, diagnosing, testing, complications and management of   thyroid disorder in pregnancy and post-partum period. It also includes neonatal morbidity due to maternal thyroid disease and future research in the field.Some of the salient recommendations are summarized here.

How to Screen for Thyroid disorder in pregnancy

(Am Thyroid Association) ?.

·                  All pregnant patients should be verbally and clinically screened for thyroid disease and use of thyroid medications. If any of the risk factors are identified, then testing for TSH is advisable. 

·                  Universal screening for low free thyroxine concentrations in pregnant women is not recommended. 

·                  Insufficient evidence also exists for Universal screening or no screening for TSH level preconception or in early pregnancy. 

 

Hypothyroid in Pregnancy.

 

·                  The reference range for serum TSH changes in pregnancy. Hence, population based trimester-specific reference range for TSH should be defined.

·                  The requirement of Levothyroxine only increases by 20-30% during pregnancy and a simple way of achieving it is to administer 2 additional tablets weekly of the patient’s current daily levothyroxine dosage.

·                  Subclinical hypothyroidism in pregnancy should be treated according to the reference range for the population and TPO status.

·                  Overt hypothyroidism should always be treated during pregnancy with Levothyroxine only, Other thyroid preparations such as triiodothyronine (T3—available abroad ) or desiccated thyroid should not be used in pregnancy.

·        TSH level tested 6 weeks postpartum and the dose adjusted. Preconceptionally diagnosed hypothyroid women (overt or subclinical) should have their T4 dosage adjusted such that the TSH value is less than 2.5 μIU/mL before pregnancy. 

.The T4 dosage in women already on replacement will routinely require a dose escalation (30% to 50%) at 4 to 6 weeks gestation in order to maintain a TSH value less than 2.5μIU/mL.
.Pregnant women with overt hypothyroidism should be normalized as rapidly as possible to maintain TSH at less than 2.5 and 3 μIU/mL in the first, second, and third trimesters, respectively.  Euthyroid women with thyroid autoantibodies are at risk of hypothyroidism and should have TSH sreening in each trimester.
.After delivery, hypothyroid women need a reduction in T4 dosage used pregnancy. Because subclinical hypothyroidism is associated with adverse outcomes for mother and the fetus, T4 replacement is recommend