Serum FSH bioactivity and response to acute gonadotrophin releasing hormone (GnRH) agonist stimulation in patients with polycystic ovary syndrome (PCOS) as compared to control groups.

OBJECTIVE

We evaluated the biological activity of FSH in the serum of women with polycystic ovary syndrome before and after acute administration of a GnRH agonist as compared to control groups.

DESIGN

FSH, oestradiol and androstenedione response to buserelin (100 micrograms s.c.) comparing seven polycystic ovary patients, six idiopathic hirsute women, 11 normal women in the follicular phase and nine normal men.

MEASUREMENTS: Rat granulosa cell aromatase bioassay in the presence or absence of polyethyleneglycol (PEG) pretreated 2% serum. Serum biological FSH (B-FSH), immunological FSH (I-FSH) and B/I ratio at times 0, 1, 2, 3, 4, 8, 12 and 24 hours. Serum androstenedione and oestradiol at times 0 and 24 hours.

RESULTS

Human gonadotrophin-free (oral contraceptive user and after FSH immunoabsorption) and PEG-pretreated serum increases the aromatase activity in response to increasing doses of purified FSH. The maximum enzymatic activity is however higher with 2% serum than with 4% serum. The amplitude of the B-FSH response to the GnRH agonist is markedly decreased in the polycystic group as compared to the group of normal women. There is also a small decrease in the I-FSH response in the polycystic women. When compared to that of normal women, the area under the curve in the polycystic ovary patients is reduced by 71% for B-FSH (P < 0.01) and by 23% for I-FSH (P < 0.05). The B-FSH and I-FSH responses in men are very small. After an initial decrease the B/I ratio returns to baseline level in normal women but remains low in the other groups. At time 24 hours, there is no significant change in the serum concentration of androstenedione but serum oestradiol, the baseline of which is significantly higher in the polycystic patients than in normal women, is also significantly higher at 24 hours (P < 0.05) in response to the pharmacological release of FSH.

CONCLUSION

The gonadotrophin-free and PEG-pretreated human serum has an inherent stimulatory effect on the rat granulosa aromatase bioassay with a higher activity at 2% serum. Acute GnRH agonist stimulation reveals a deficiency in the FSH response in polycystic ovary patients. The greater deficit in B-FSH than in I-FSH would indicate a possible modification in the FSH isoforms in this syndrome. The meaning of this observation for the understanding of the physiopathology of the polycystic ovary syndrome remains to be evaluated.