Before perimenopause or menopause, the vagina is usually moist with skin that is pink from abundant blood vessels. There are multiple folds of extra skin and mucous secreting sebaceous glands that can produce moisture quickly during sexual excitement.
When estrogen is lost the skin becomes thin, pale, and dry. The vagina narrows and shortens. The opening to the vagina, called the introitus, can narrow, as well—especially when penetrative sex is not practiced.
The vaginal skin can become so thin that small breaks in the blood vessels (now far fewer in number) can occur, the once abundant folds of extra skin disappear, and the vagina loses much of its capacity to expand when needed.
The sebaceous glands may remain but they do not function well. The natural lubrication women experience with stimulation is both lessened and delayed.