The study looked at how a part of the brain called the paraventricular nucleus (PVN) regulates thyroid hormone levels in rats. They found that rats with PVN lesions had lower levels of thyroid-stimulating hormone (TSH) compared to rats without lesions when they were hypothyroid. This suggests that the PVN plays a major role in controlling TSH levels in response to low thyroid hormone levels. Additionally, the levels of certain genes related to TSH production were also affected by the PVN lesions. Overall, the study shows that the PVN is important for regulating TSH levels in the body.