ID and PTU-induced hypothyroidism delayed the eye opening in offspring. The ratio of iodine-deficient and 15 ppm PTU-treatment pups within a litter with both eyes open was significantly lower than controls on PN17 and PN18. Each bar represents the mean ± SEM (control group: n = 6; 5 ppm treatment group: n = 6; 15 ppm treatment group: n = 6; iodine-deficient group: n = 7). *P < 0.05, as compared to control. #P < 0.05, as compared to 5 ppm PTU-treatment group. ΔP < 0.05, as compared to 15 ppm PTU-treatment group.