Human Reproduction, Vol 12, 1156-1164, Copyright © 1997 by Oxford University Press
AP Cheung, JK Lu and RJ Chang
In polycystic ovary syndrome (PCOS), increased luteinizing hormone (LH)
pulse frequency has been attributed to either the hypothalamic
gonadotrophin-releasing hormone (GnRH) pulse generator or ovarian oestrogen
feedback. To address this issue, a detailed examination of pulsatile LH
secretion was undertaken during recovery from GnRH agonist (GnRHa)
suppression. Each of six women with PCOS and six normal ovulatory women
received daily GnRHa treatment for 14 weeks. Frequent blood samples were
collected and assayed for gonadotrophins, androgens and oestrogens before,
during and up to 4 weeks after treatment. Women with PCOS had higher basal
LH pulse frequency and amplitude and increased serum concentrations of LH,
androstenedione, testosterone and oestrone than controls. After 3 months of
GnRHa treatment, all these parameters were suppressed with no differences
observed between the two groups. One week after cessation of GnRHa, LH
pulse frequency promptly returned to pre-treatment range with no
between-group differences noted, whereas LH pulse amplitude, serum
gonadotrophins and ovarian steroids remained maximally suppressed and
equivalent in the two groups. Subsequent LH pulse frequency remained
constant while LH pulse amplitude and circulating concentrations gradually
increased in parallel with a return of serum oestrogen to pre-treatment
values. Despite comparable resumption of LH secretion in the two groups,
corresponding androgen concentrations in women with PCOS were greater than
those of normal ovulatory women. Thus, the immediate restoration of LH
pulse frequency after discontinuing GnRHa treatment is largely independent
of ovarian oestrogen production and reflects primacy of the GnRH pulse
generator in determining basal LH pulse frequency. Equivalent LH pulse
frequency rates in the two groups during the recovery period do not suggest
an intrinsic hypothalamic-pituitary hyperactivity in PCOS.
ARTICLES
Pulsatile gonadotrophin secretion in women with polycystic ovary syndrome after gonadotrophin-releasing hormone agonist treatment
Department of Obstetrics and Gynecology, University of California, Los Angeles, USA.
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