Determining the etiology of overt hyperthyroidism during pregnancy or lactation

TRAb: thyrotropin receptor antibodies; TSI: thyroid-stimulating immunoglobulins; TBI/TBII: thyrotropin receptor-binding inhibitory immunoglobulin; hCG: human chorionic gonadotropin; TSH: thyroid-stimulating hormone; T4: thyroxine; T3: triiodothyronine.
* The presence of orbitopathy (ophthalmopathy) alone may be sufficient to diagnose Graves' disease.
¶ Moderate to severe hyperthyroidism: TSH values are generally below 0.05 mU/L with elevations in trimester-specific free T4 concentrations and/or total T4 and T3 concentrations that exceed the upper limit of normal for pregnant patients. Obtain endocrinology consultation if interpretation of thyroid tests is unclear.
Δ We obtain TSI after diagnosis of Graves' disease to monitor for fetal or neonatal Graves' disease.
◊ Radioactive iodine studies are contraindicated during pregnancy and breastfeeding.
§ Gestational transient thyrotoxicosis occurs in the first trimester, and symptoms (if present) and thyroid hyperfunction (which is usually mild) subside as hCG production falls (typically 14 to 18 weeks gestation).