Abstract
Background: Effects of soy-containing infant formulas on the thyroid
gland is not clear We aimed to evaluate the effects of infant formulas
with different quantities of soy content on the functional and
histopathological characteristics of the thyroid gland. Method:
Twenty-eight female Sprague-Dawley rats were divided into four groups.
Group 1 was fed with standard pellet rat food (8g/day); Group 2 soy-free
infant formula (8g/day); Group 3 low-dose (1.12g/100ml) soy-containing
formula (8g/day), and Group 4 high-dose (2.64g/100ml) soy-containing
formula (8g/day). Blood samples were collected from the subjects on day
0, 30, 60, and 90 to evaluate thyroid functions. All subjects were
sacrificed on day 90. Thyroid glands were excised and examined
histopathologically. Results: Serum levels of free T3, free T4, TSH,
anti TPO, and anti TG were significantly higher in Group 4 compared to
other groups (p<0.001,
p<0.01,p<0.001,p=0.002). No differences were found
in the histopathological findings between the groups. Conclusion: Infant
formulas with high soy content induce hyperthyroidism with high TSH
levels. High levels of anti TPO and anti TG suggest that observed
changes might have occurred via inflammatory mechanism.