The key laboratory mark for making differencial diagnosis between primarily congenital hypothyroidism and hypothyroidism caused by hypoplasia of hypothalamas-pituitary
A
serum free triiodothyronine and free thyroxine
B
serum total triiodothyronine and free thyroxine
C
thyroid-stimulating hormone
D
antithyroglobulin antibody
E
thyrotropin-releasing hormone