Describe the endocrine basis of SAD. Identify the affected hormone (1 mark) and explain how problems with this hormone due to the lack of sunlight affect individuals with SAD. (2 marks) SAD is a Seasonal Affective Disorder.  I found the hormone and the gland that affects this disorder are Melatonin and the pineal gland.  In the first part it says describe the endocrine basis of SAD. anot sure what theyre asking me to do. help appreciated thank you :)