Hypothyroidism in Pregancy-Diagnosis & treatment Preg outcome.

  Courtesy http://online.liebertpub.com/doi/pdfplus/10.1089/thy.2016.0457

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 geographical area. (population based TSH in euthyroid men & women is a bit high as our drinking water is deficient in iodine though common slat is fortified with  iodine )..Even in India the sub Himalayan states are deficient in iodine so local TSH will be a bit high

. 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. These 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.

·                     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 though such increment are not approved by all international agencies .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) or desiccated thyroid should not be used in pregnancy.

·                     TSH level tested 6 weeks postpartum and the dose adjusted.

Iodine requirements in pregnancy and before conception

·                     All pregnant women should have approximately 250 μg iodine daily. 

·                     All women who are planning to become pregnant should supplement the diet with daily 150 μg of iodine, optimally 3 months before the conception except women with already existing hyper or hypothyroidism.

·                     Excessive iodine supplements and sustained dietary intake above 500 μg daily should be avoided during pregnancy.

Subclinical hypothyroidism.

·                     All Euthyroid but TPO or Tg(thymoglobulin)  antibody positive pregnant women should have serum TSH concentration performed at time of pregnancy confirmation, and every 4 weeks through mid-pregnancy. These women should not be treated with thyroxine just to prevent RPL or preterm delivery.

Infertility and Thyroid disorders.

·                     All infertility patients should have their thyroid function done and only women with overt hypothyroidism should be treated with levothyroxine. 

·                     Evidence is insufficient for supplementing levothyroxine to all women with subclinical hypothyroidism to improve fertility.

·                     Women with subclinical hypothyroid undergoing IVF or ICSI should be treated with levothyroxine. The goal of treatment is to achieve a TSH concentration TSH <2.5.

Hyperthyroidism in pregnancy.

·                     Managing Hyperthyroidism in pregnancy is very complicated issue. Radionuclide scintigraphy or radioiodine uptake determination is contraindicated in pregnancy.

·                     Methimazole (MMI) nor propyl thiouracil (PTU) is safe during pregnancy and should be immediately stopped once the pregnancy is confirmed because of its teratogenic potential. If at all required than PTU is preferred over MMI till 16 weeks in the lowest effective dose.

·                     The fetus should be closely looked at for Goiter or hypothyroidism during the second half of pregnancy.

·                     Thyroidectomy in Graves’ disease in only indicated in specific situation and should follow the recommendations of ACOG to schedule any surgery during pregnancy.

Hyperthyroidism in pregnancy.

·                     Managing Hyperthyroidism in pregnancy is very complicated issue. Radionuclide scintigraphy or radioiodine uptake determination is contraindicated in pregnancy.Methimazole (MMI) nor propyl thiouracil (PTU) is safe during pregnancy and should be immediately stopped once the pregnancy is confirmed because of its teratogenic potential. If at all required than PTU is preferred over MMI till 16 weeks in the lowest effective dose.

·                     The fetus should be closely looked at for Goiter or hypothyroidism during the second half of pregnancy.

·                     Thyroidectomy in Graves’ disease in only indicated in specific situation and should follow the recommendations of ACOG to schedule any surgery during pregnancy.