Figure 1.

Fluctuations of thyroid hormone levels in normal pregnancies and non-pregnant women. From 8–14 to ≥37 weeks, the concentrations of maternal serum FT3 and FT4 continuous declined, while TSH was increased in normal pregnant women. From the ages of 20–40 to 56–85, the TSH concentration in non-pregnant women increased, but no trend for FT3 and FT4 was observed. 1, 8–14 weeks; 2, 15–20 weeks; 3, 21–36 weeks; 4, ≥37 weeks in pregnant women and 1, age 20–40; 2, age 41–55; 3, age 56–85 years in non-pregnant women.