Abstract
The functional organisation of the hypothalamic-pituitaryovarian axis is reviewed.
A description is given of two newly developed radioimmunoassays
for the measurement of 17p -oestradiol and 1 7^-ethinyloestradiol in
peripheral plasma. The characteristics of these assay methods qua
sensitivity, specificity, accuracy and reproducibility are described.
The effects of exogenous oestrogen administration on pituitary
gonadotrophin and gonadal steroid secretion have been studied in normal
women during the early-mid follicular phase of the cycle, in intact
adult men and in male pseudohermaphrodites (testicular feminization,
U pure gonadal dysgenesis). Unlike in normal women and XY pure gonadal
dysgenesis, oestrogen treatment did not stimulate LH release in intact
adult men or patients with testicular feminization. Evidence is presented
which suggests that oestrogen may directly inhibit testicular testosterone
secretion in normal men.
In adolescents with anovulatory dysfunctional uterine bleeding
it was demonstrated that the failure to ovulate in this condition may
be attributed to an inability of these patients to release an adequate
amount of LH in response to oestrogen.
Long-term serial measurements of pituitary gonadotrophins and
ovarian steroid hormones in perimenopausal women indicated that dysfunctional uterine bleeding in this age group may have a variety of
causes. Several abnormalities in pituitary gonadotrophin secretion were
found including failure to release LH in response to endogenous or
exogenous oestrogen, monotropic elevation of FSH during ovulatory cycles
with short follicular phase, and increases in both FSH and LH during
anovulatory cycles with long intermenstrual intervals. It is suggested
that these endocrine abnormalities during the menopausal transition may
arise from a change in hypothalamic-pituitary sensitivity to steroid
feedback or from a progressive decline in the ovarian secretion of a
hypothetical FSH-release inhibiting substance (FRIS) produced by the
growing follicle.
In patients with polycystic ovary syndrome it was demonstrated
that positive and negative feedback are intact in this condition and
that pituitary EH secretion under basal conditions and in response to
ERF was influenced by the pattern of ovarian activity during the U to 6
week period which preceded the measurement of this hormonal parameter.
In patients with secondary amenorrhoea elevated basal 17-fluorogenic corticosteroid and androstenedione levels were found. In addition,
underweight patients had elevated basal growth hormone levels, markedly
suppressed basal gonadotrophin levels and impaired pituitary FSH and EH
release after ERF-injection. Growth hormone and prolactin secretion in
response to insulin-induced hypoglycaemia were also impaired in these
patients. Low basal 17Β-oestradiol levels were found in patients with
low FSH and EH but also in women with elevated prolactin levels who had
normal peripheral gonadotrophin levels. Clomiphene responsiveness was
related to the basal gonadotrophin and prolactin concentrations. It is
hypothesised that the abnormalities in hypothalamic-pituitary function
in women with secondary amenorrhoea may be a result of selective
neurotransmitter deficiencies.
