"Empty follicle" syndrome is a description/name of a condition that is found when no eggs are retrieved from obviously adequate sized follicles. It can occur at any age, but seems to be more prevalent the older one gets. So, a woman in her 40's could still have regular menstrual cycles and ovulation, but no egg will be ovulated so pregnancy does not occur. With IVF, we find this when we go to retrieve and get no eggs back. It is thought that this is the "normal natural condition" in the aging ovary. A woman essentially runs out of eggs. However, that does not seem to be the case in younger woman, since younger women stil have a full complement of eggs. So, "running out of eggs" does not seem to be the whole answer.
　
I have had several cases of empty follicles in both younger and older women. In the younger patients, I have concluded that they did not get adequate HCG stimulation. Previously I had used a generic HCG and worried that it was not produced properly or suffered some type of inactivation in shipping or storage. I therefore switched to Ovidrel. Since then, the incidence of empty follicles has been resolved except in a couple of exceptions. I had two moderately obese young woman have a very poor retrieval despite lots of follicles (both were PCOD patients). By poor retrieval, I mean that there were either no eggs or we only retrieved 1 or 2 eggs despite 25+ follicles. They had given the Ovidrel as instructed, into their belly. In the subsequent cycle, I had them give it in the back of the arm where there was some fatty tissue but much less than the abdomen. They then had good retrievals. This lead me to suspect that HCG stimulation was the problem, and that the increased fatty layer of the abdomen did not allow adequate absorption of the HCG, therefore the eggs did not release to be retrieved.