Endocrine system help

[dizzyd]

I need some help with the endocrine sytsem I have a few question that I do not undrestand. like 1-How are circulating(blood) hormone levels controlled to achieve the desired level(of response)? 2- How do hormones change the activity of target tissues/organs? Waht are the differences between how steroid & peptide hormone do in the target tissue/organ to change its activity? Can anyone help?