Analysis of the hypothalamic–pituitary–thyroid axis in the TR-β
mutant mice. (a) Schematic diagram of the axis and
feedback loop in normal and TR-β mutant animals. The disruption in
feedback at the hypothalamic TRH neuron is presumed but is not proven.
(b–f) Serum total and free thyroid hormone and
TSH levels (mean ± SEM) in serum from male mice at 4 weeks of
age, as determined by RIA. +/+, n = 11; mut/+,
n = 14; mut/mut, n = 6;
TR-β −/+, n = 6. #, Below detection limit.
**, P < 0.01 and
***, P < 0.001 vs. +/+ by
t testing.