The purpose of this research study is to determine whether melatonin taken every night can
affect blood levels of estrogen or IGF (insulin-growth factor levels). Both IGF and estrogen
are normally produced in the body and may influence breast cancer risk. Melatonin is also
naturally produced in the body. Laboratory studies have shown that melatonin may decrease
cancer growth and influence estrogen and IGF levels. Melatonin's effects on sleep, hot
flashes, and mood will also be measured.