Establishment and Characterization of SCH Rat Model

Establishment of the SCH rat model refers to the previously literature [13 (link)].The rats were injected with 3% pentobarbital sodium (0.1 mL/100 g) and underwent thyroidectomy, while Sham group rats underwent sham thyroid surgery. The rats were fed normally for 4 w after operation, then the blood was collected from the retroorbital venous plexus, and serum TSH and TT4 were detected. When serum TSH levels were higher than that in Sham group, the TT4 levels were lower than that in Sham group, confirming the successful establishment of the SCH rat model. Four weeks after surgery, rats in the SCH group were injected subcutaneously with L-thyroxine (L-T4, Sigma, USA) 1.0 μg/100 g/day on the neck. Sham group rats were injected subcutaneously with physiological saline (50 μL/100 g/day) on the neck. Calcium lactate (0.1% w/v) was added to the drinking water for all rats after surgery. Nine days later, all rats were mated with normal male rats (male: female = 1: 2). The pregnant rats were then kept in single cages until delivery. The day of vaginal plus was confirmed by microscopic observation and designated as E0. Serum and tissue samples were collected at E16, E18, P5 and P10. At the end of the experiment, all rats were anesthetized with pentobarbital (50 mg/kg, intraperitoneal) and euthanized by thoracotomy and hearts removal.