Figure 8. Between-Method TSH Variability Impacts Thyroid Testing in Pregnancy. The figure is a summary of 43 published studies showing the upper and lower TSH reference limits (2.5–97.5 %) measured in each trimester of pregnancy by four different methods – Abbott (1), Beckman (2), Roche (3), and Siemens (4). The data shows the expected trend for a lower TSH in the first trimester, resulting from thyroidal human chorionic gonadotropin (HCG) stimulation of thyroxine, which is maximal in the first trimester. The data is re- drawn with permission from reference 156.