The hormones secreted into the bloodstream during times of stress are

The answer to this question would be: cortisol

Cortisol is a hormone secreted by the adrenal glands that were located near to kidney. The hormone is secreted into the bloodstream when the organism facing stress to prepare for "fight or flight" condition. This hormone will increase metabolism and increase blood glucose level. But in long term it can cause many diseases as it lower immune system, increase blood pressure, and increase cholesterol.