Thyroid and Pregnancy in Tehran, Iran: Objectives and Study Protocol

Thyroid dysfunction is the second most common endocrine disease in females of reproductive age. There are controversial data on the adverse effect of subclinical thyroid dysfunctions on adverse feto-maternal outcomes.

The current study aimed to identify the prevalence of thyroid dysfunction during pregnancy and to assess the effectiveness of treatment with levothyroxine on pregnancy outcomes of females with thyroid autoimmunity with or without subclinical thyroid dysfunction in Tehran, Iran.

The study encompassed two phases: 1) a population based cross sectional study using a cluster sampling method that screened first trimester pregnant females for thyroid disorders, 2) a double-blind randomized clinical trial to determine the effectiveness of levothyroxine on adverse pregnancy outcomes in females with thyroid autoimmunity with or without subclinical thyroid dysfunction. Pregnant females were assessed at their first prenatal visit for serum TSH, T4, T-uptake, TPOAb and urinary iodine following which they were classified as: 1) normal, 2) subclinical TPOAb negative and 3) subclinical/euthyroid TPOAb positive. Females in groups two and three were randomly divided into two groups: group A was treated with levothyroxine (LT4), and group B did not receive any treatment. There was a follow-up program for participants and rates of adverse pregnancy outcomes in the treated and untreated groups were measured.

Results of the study provided reliable information regarding the prevalence of thyroid dysfunction among females in Tehran using universal thyroid screening, along with identification of the iodine status of their community. The study aimed to determine whether LT4 treatment exerts beneficial effects in females without overt thyroid dysfunction.