Thyroid hormones are responsible for regulating energy in the body. It can influence you to either take a nap or go for a run. The animals in hibernation mode have low levels of thyroid hormones hence they sleep for a longer duration of time. Thyroid hormones respond when they receive signals from the brain. They coordinate cells according to the instructions received that are generally in sync with other functions of the body. People with a low level of thyroid hormones will feel exhausted easily.