Efficacy of low dose purified FSH in ovulation induction following pituitary desensitization in polycystic ovarian syndrome.

OBJECTIVES

We evaluated the efficacy of ovulation induction using purified FSH in either low dose or conventional dosage in patients with polycystic ovarian syndrome. We assessed whether gonadotrophin measurement by radioimmunoassay or immunoradiometric assay is a better indicator of whether pituitary desensitization with a GnRH agonist (Zoladex) has occurred.

DESIGN

Two different protocols were used. Pituitary desensitization was carried out with a GnRH agonist (Zoladex, ICI Pharmaceuticals UK). The patients were then randomized into one of two treatment groups. Conventional dose protocol: Patients commenced with a daily FSH (Metrodin, Serono Laboratories Ltd, UK) dose of 75 units for at least 7 days. The FSH dose was then increased, if necessary, based on ultrasound scans and plasma oestradiol (E2) levels in 75-unit increments. Low dose protocol: The same protocol was used except that the starting dose of FSH was 37.5 units daily with increments of 37.5 units.

RESULTS

Low dose protocol (six patients, six cycles). There was a high incidence of multiple follicular development (10.3 +/- 5.6 (+/- SD) follicles, 5.0 +/- 3.8 follicles > 14 mm in diameter). Three cycles resulted in ovulation, one was anovulatory and two patients underwent gamete intrafallopian transfer due to multiple follicular development. Conventional dose protocol (seven patients, eight cycles). Again there was multiple follicular development (10.1 +/- 8.6 follicles, 2.0 +/- 2.3 > 14 mm). Three cycles were ovulatory, one anovulatory, three abandoned due to multiple follicular development and one underwent gamete intrafallopian transfer with the development of severe hyperstimulation necessitating steroid therapy. There was no difference between the two protocols in the number of days of FSH administration (low dose protocol 26 +/- 6.5, conventional dose protocol 23 +/- 8.1 days), the total number of units of FSH given per patient was 2844 +/- 1816 vs 2635 +/- 1726. The peak E2 level (pmol/l) during FSH treatment was 3193 +/- 662 vs 2389 +/- 3099 and the rate of increase in the FSH dose in ampoules of Metrodin per day was 0.058 +/- 0.03 vs 0.057 +/- 0.03. All patients were 'downregulated' (E2 < 70 pmol/l) prior to ovulation induction. However, gonadotrophin levels (IU/l) were 4.3 +/- 1.5 (LH) and 2.8 +/- 1.2 (FSH) by radioimmunoassay and LH was unchanged throughout FSH treatment whereas LH measured by immunoradiometric assay was < 1.0 IU/l prior to ovulation induction and remained so throughout. The mean LH radioimmunoassay to immunoradiometric assay ratio was 6.2 +/- 2.1.

CONCLUSIONS

We conclude that regardless of the starting dose the use of pure FSH in patients with polycystic ovarian syndrome whose LH has been completely down regulated may be associated with multiple follicular development and a poor outcome. LH measured by radioimmunoassay is not a good indicator of whether pituitary densensitization has occurred but LH measured by immunoradiometric assay appears to be. These results strongly suggest that a basic minimum amount of LH is necessary for normal ovulatory development.