College students are notorious for having a reversed day-night schedule. They stay up all night and sleep during the day. This alteration changes what hormone levels?

A) melatonin
B) leptin
C) growth hormone
D) testosterone in males; estrogen in females
E) prostaglandins

Melatonin is a hormone that is regulated by the circadian rhythm, which controls sleep and wake cycles. Exposure to light suppresses the production of melatonin, and in college students who stay up all night and sleep during the day, melatonin levels may be disrupted, leading to difficulty falling asleep at night and feeling drowsy during the day.