Modulating Thyroid Hormone Levels in Adult Mice: Impact on Behavior and Compensatory Brain Changes

Figure 2

Serum and tissue levels of T4. Wild-type mice were treated with levothyroxine or a PTU/Met combination for four months, starting at 14 months old. (a) Thyroxine treatment led to a large increase in serum T4 by two months, then increased even further by four months. There was a significant decrease in circulating T4 in animals treated with PTU/Met by two months. This was maintained at four months, although there was no additional change. Note that this graph has a logarithmic y-axis. (b) There was a small increase in brain T4 in thyroxine-treated mice, but PTU/Met treatment did not have an effect. (c) Unlike T4, there was no significant change in serum T3 at two months, although there was a small increase at four months with thyroxine treatment. PTU treatment did not lead to a change at either time point. Brain levels of T3 (d) were unchanged in both treatment groups. Control = 7 M/6 F, thyroxine = 5 M/5 F (heart), and PTU/Met = 5 M/8 F. .

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