Physiology: Healthy and atretic follicles: vaginosonographic detection and follicular fluid hormone profiles

The health status of human preovulatory follicles was prospectivelystudied by non-invasive transvaginal ultrasound. Daily ultrasoundscans were performed from the time when the follicle measured15 mm in diameter until formation of corpus luteum or oocyteretrieval. Based on the ultrasound scans two types of follicleswere defined: type A follicles showed a cloud visualized asa cone projecting into the follicular fluid with the base ofthe cone positioned on the follicle wall. A light spot seenat the tip of the cloud in the majority of scans was presumedto be the oocyte-cumulus complex. Type B follicles showed anecho free space without a cloud. Two groups of infertility patientswere studied: Group I received intrauterine insemination; 106patients undergoing a total of 263 cycles (188 spontaneous cyclesand 75 clomiphene citrate cycles). Group II received in-vitrofertilization (IVF); 22 patients undergoing a total of 52 cycles(31 spontaneous cycles and 21 clomiphene cycles). In the firstgroup, the ovulatory potential of the follicle is associatedwith the ultrasound characteristics. From the IVF patients thefollicular fluid was harvested and assessed for the free concentrationof the following steroids: oestradiol, progesterone, testosteroneand androstendione. The endocrine health status of the folliclewas associated with the ultrasound characteristics of the follicle.In patients of group 1, 288 type A follicles ovulated out ofa total of 298 follicles (97%). None of the type B folliclesovulated (0/14). In patients of group II, oocytes were obtainedin 79% of the type A follicles (50/63), whereas 7% of the typeB follicles yielded an oocyte (1/14). The follicular fluid hormoneprofile showed significantly lower free oestradiol, free oestradiol/testosteroneratio and oestradiol/androstenedione ratio and higher free testosteroneand free androstenedione in type B follicles compared to typeA follicles. The hormone status and the high oocyte recoveryrate suggest that type A follicles are healthier than type Bfollicles, which seem to have undergone atretic changes. Itis concluded that non-invasive transvaginal ultrasound witha good degree of accuracy predicts the health status of preovulatoryfollicles. Healthy follicles have a cloud with a light spotat the tip, whereas almost all atretic follicles lack this characteristic.