Genesis of PCO -What happens in ovaries ??

 

Genesis  of PCOS:

      Elevated androgen leads to recruitment of multiple follicles in the ovaries. But all these follicles do not become dominant. The antral follicles produce oestrogen and excess androgen also is converted to oestrogen. These lead to high oestrogen levels in absence of mature follicle. This gives negative feedback to FSH, which interferes with follicular growth, and a positive feedback to LH, which causes luteinization of these immature follicles and follicular atresia, with conversion of granulose cells to theca cells that contribute to stroma.  

In the early phase of the disease the stroma becomes denser in parts and when anovulation continues, whole stroma becomes echogenic, leading to a generalize cystic pattern (GCP) of PCO. As the disease progresses, follicles are pushed to the periphery and then not only the stromal density but the stromal volume also increases, leading to enlargement of the ovary leading to peripheral cystic pattern (PCP) of PCO.

 

This means that from multicystic cystic ovaries i.e. ovaries normal in size having multiple follicles of various sizes and normal stroma- which is a normal appearance in adolescence to GCP PCO and PCP PCO is a process of evolution as a result of high basal androgen levels and chronic anovulation in these females. This explains not only the variability in the size of the ovaries but also the variability  in the number of antral follicles in PCOS patients having oligo-ovulation and Hyperandrogenism.

Predominant hyperechoic stroma

      Stromal abundance therefore is the most reliable and key factor for the diagnosis of PCOS. This abundance can be known by increased stromal echogenecity. Polycystic ovaries show a hyperechoic stroma but assessment of this hyperechogenecity is subjective not only to the operator but also to equipment settings.^10,11 Therefore a more objective or reproducible criteria is required for assessment of stromal density and this is done by measuring ovarian area and stromal area on 2D ultrasound and ovarian volume and stromal volume on 3D US. Ovarian area of 5.3 cm² on strict longitudinal ovarian section and stromal area of 4.6 cms² has high sensitivity and specificity for PCOS.⁴ But stromal area/ovarian area ratio has been found to be even more efficient for diagnosis of PCOS.