Some women do start experiencing hormonal changes of perimenopause in their late 30's or early 40's. So it may explain your wife's symptoms. Some gynecologic treatments can also disrupt natural hormone production.
Hello~It could be the start of "Peri-menopause", I started mine when I was 35, but I did not miss a period until my 50's. I always had hot flashes even when I was not near menopause. I would ask your gyn for some blood work for hormones and also, get some "Bio-identical" progesterone cream, this type of cream is formulated to be exactly like your own body's progesterone, and it has no side effects, it helps many hormonal issues in all ages of women, even teens can use it. You can get it at any good, reputable health food store or there are many resources on-line as well. Also, read the book called "What the doctors won't tell you about Peri-Menopause" by Dr Lee, he was the pioneer in bio-identical hormones and there is a wealth of info in that book. His other book, "What your doctor won't tell you about menopause" is excellent as well. Both can be purchased on-line or in most bookstores, many health food stores sell them as well.