Thyroid Hormones Independently Regulate Brain's Thyrotropic Center mRNA Levels
Thyroid hormones can reduce the production of a hormone called TRH in the brain. Scientists wanted to see if this effect depends on the pituitary gland or another hormone called TSH. They studied rats that had their pituitary glands removed and found that thyroid hormones still decreased TRH levels in the brain, even when TSH was replaced. This shows that the control of TRH production by thyroid hormones in the brain does not need the pituitary gland or TSH.