Abolishment of the positive feedback mechanism: a criterion for temporary medical hypophysectomy by LH-RH agonist

Induction of ovulation: historical aspects

The cornerstone of the conquest of infertility was laid in the beginning of this century. It took, however, nearly 80 years of work of many scientists from all over the globe to slowly unravel the puzzle of nature's most guarded secret, the control of the reproductive processes. The estimated population size of women between the ages 19 and 34 years in the developed world in 1990 will be about 130 million. If we assume that at least 8% will be infertile, then the pool of the infertile population will be above 10 million, with about 700,000 new patients entering this pool every year between the years 1990 and 1995. In the past only about 40% of infertile patients benefited from ovulation induction regimens. With the advent of assisted reproduction this population increased to about 80%. With the use of gonadotrophins for induction of superovulation in normally ovulating women conceptual changes in treatment regimens and monitoring schemes had to be introduced. It is obvious that the primary task of infertility clinics is to diagnose the main cause (or causes) of infertility in each couple in order to be able to institute appropriate therapy within a reasonable time. We have attempted to review briefly the regulation of follicular development, particularly with regard to new findings demonstrating the potentiating effect of growth hormone and/or various growth factors on ovarian sensitivity to FSH. This new knowledge, as well as availability of potent GnRH analogues, will evidently refine our clinical approach to treatment of functional infertility. Continuous advances in the understanding of mechanisms regulating reproductive processes and the better recognition of underlying causes of infertility will lead to the optimal choice of first-, second- and third-line routine therapies which will apply to the majority of patients. Furthermore, it will become possible to design tailor-made ovulation-inducing protocols for specific patients who do not respond properly to the routine treatment.

Pulsatile secretion of prolactin and luteinizing hormone and their synchronous relationship during the human menstrual cycle

Recent investigations have demonstrated the pulsatile nature of prolactin (PRL) secretion and the synchronous relationship between PRL and LH pulses in normal and hypogonadal women. The present study was designed to confirm this synchrony and to investigate the characteristics of PRL pulses at different stages of the menstrual cycle. Blood samples were obtained at 10-minute intervals, beginning at 10.00 hours, for a duration of 4-7 hours, from women during the follicular (n = 11), preovulatory (n = 2) and luteal (n = 10) phases. Detectable pulses in plasma PRL concentrations were present in almost all subjects during each phase of the cycle. During the total 121-hour blood sampling throughout the 3 phases, 62 PRL pulses and 74 LH pulses were detected and about 80% of the PRL pulses were observed to coincide with LH pulses. The mean (+/- SD) pulse frequency of PRL was significantly lower during the luteal phase (0.28 +/- 0.17 pulses/hour) than during the follicular (0.64 +/- 0.25 pulses/hour) and preovulatory (0.72 +/- 0.16 pulses/hour) phases, while the mean pulse amplitude of PRL was significantly greater during the luteal phase (6.8 +/- 2.3 ng/ml) than during the follicular (3.6 +/- 1.2 ng/ml) and preovulatory (4.1 +/- 1.0 ng/ml) phases. These changes in pulse frequency and amplitude were also observed in LH pulses between the follicular and luteal phases, except at the LH surge, when LH pulse amplitude increased markedly, but that of PRL did not alter. Furthermore, a positive linear correlation between the pulse frequency of PRL and LH (r = 0.74, p less than 0.001) was found throughout the 3 phases of the cycle. These results demonstrate that a marked degree of synchrony between PRL and LH pulses is observed during the menstrual cycle and suggest that the frequency and amplitude of PRL pulses vary from the follicular to luteal phases, except at the LH surge, almost in parallel with those of LH pulses.