Ovarian follicle counts – not as simple as 1, 2, 3

Debate The functional life span of the ovaries is dictated in large part by the number of oocytes present, a number that is known to decline precipitously during both fetal development and postnatal life. Furthermore, studies from numerous laboratories have shown that exposure of the ovaries to a variety of pathological insults, such as anticancer therapies and environmental toxicants, accelerates oocyte and follicle depletion, consequently hastening the time at which ovarian failure is observed. Accordingly, over the past several years a tremendous amount of research effort has been expended to uncover the genetic and molecular mechanisms responsible for determining the size of the follicle reserve endowed at birth as well as the rate at which this stockpile of follicles is subsequently depleted [reviewed in [1,2]]. Since, however, there are no known serum markers that can be used to accurately estimate the number of follicles in the ovaries – in particular follicles at the earliest stages of development (primordial, primary, small preantral) – some type of histomorphometric evaluation of the ovary is generally employed.