Thyroid dysfunction and thyroid autoimmunity in euthyroid women in achieving fertility

OBJECTIVE: Thyroid disease is the second most common endocrine condition in women of childbearing age. Thyroid hormones are involved in control of menstrual cycle and in achieving fertility affecting the actions of follicle-stimulating hormone and luteinizing hormone on steroid biosynthesis by specific triiodothyronine sites on oocytes; therefore, affect all aspects of reproduction. It remains controversial if pregnant women should be screened for thyroid dysfunction. Purpose of this review was to examine recent studies on the assessment of thyroid dysfunction in pregnancy, its treatment and newly perspective of thyroid autoimmunity in pregnant euthyroid women in achieving fertility. METHODS: An electronic search was conducted using the internet medical databases: Medline/PubMed, EMBASE, EBSCO, and the Cochrane library. RESULTS: Thyroid gland faces great challenge in pregnancy when many hormonal changes occur. Precondition for normal follicular development and ovulation is pulsate gonadothropin realizing hormone secretion. Thyroid dysfunction in pregnancy is classified as forms of hypothyroidism (positivity of thyroid autoantibody, isolated hypothyroidism, and subclinical or overt hypothyroidism), hyperthyroidism, and autoimmune disease, but also thyroid nodules and cancer, iodine insufficiency and postpartum thyroiditis. These conditions can cause adverse effects on mother and fetus including pregnancy loss, gestational hypertension, or pre-eclampsia, pre-term delivery, low birth weight, placental abruption and postpartum hemorrhage. There is an evidence that thyroid autoimmunity, in thyroid dysfunction adversely affects conception and pregnancy outcomes, but it is unclear what impact has isolated eumetabolic thyroid autoimmunity in achieving fertility, especially in women undergoing in vitro fertilization. Treatment of euthyroid pregnant women with positive thyroid peroxides antibodies is still controverse, but not few studies show that levothyroxine substitution is able to lower the chance of miscarriage and premature delivery. CONCLUSIONS: Further randomized trials are needed to expand our knowledge of physiologic changes in thyroid function during the pregnancy and to reveal mechanisms by which thyroid autoimmunity in euthyroid women affect fertility, especially the success of assisted reproductive technology in achieving the same and validity of levothyroxine administration in thyroid autoimmunity positive women.