Evidence for a specific role of GnRH pulse frequency in the control of the human menstrual cycle

Estradiol action in the female hypothalamo-pituitary-gonadal axis

It has now been about a century since a flurry of discoveries identified first the pituitary, then more specifically the anterior pituitary and soon thereafter the central nervous system as components regulating gonadal and downstream reproductive functions. This was an era of ablation/replacement designs using at first rudimentary and then increasingly pure preparations of gonadal and pituitary "activities" or transplanting actual glands, whole or homogenized, among subjects. There was, of course, controversy as is typical of lively and productive scientific debates to this day. The goals of this commentary are to briefly review the history of this work and how the terms referring to interactions among the components of the hypothalamo (as the central neural component was soon associated with)-pituitary-gonadal (HPG) axis evolved, and then to question if the current terms used have kept up with our understanding of the system. The focus in this review will be the actions of estradiol primarily upon the hypothalamus. Important actions of progesterone on the hypothalamus as well as both steroids on the pituitary response to hypothalamic factors are both acknowledged and largely ignored in this document, as are any sex differences as we focus on females.

Female Athlete Triad: Future Directions for Energy Availability and Eating Disorder Research and Practice

Despite more than 3 decades of research on the Female Athlete Triad, research gaps remain. Although low energy availability (EA) is the key etiologic factor in the Triad and the pathways to low EA are varied, its effects can be modified by several factors. Accurate screening, diagnosis, and treatment of disordered eating are a challenge; however, recent techniques combined with novel educational and behavior interventions prove promising. Recently published practice-based guidelines have helped to translate Triad science and should improve as they are refined. This article identifies the current state of research and distinguishes areas that require further investigation.

Evidence that the arcuate nucleus is an important site of progesterone negative feedback in the ewe

There is now considerable evidence that dynorphin neurons mediate the negative feedback actions of progesterone to inhibit GnRH and LH pulse frequency, but the specific neurons have yet to be identified. In ewes, dynorphin neurons in the arcuate nucleus (ARC) and preoptic area (POA) are likely candidates based on colocalization with progesterone receptors. These studies tested the hypothesis that progesterone negative feedback occurs in either the ARC or POA by determining whether microimplants of progesterone into either site would inhibit LH pulse frequency (study 1) and whether microimplants of the progesterone receptor antagonist, RU486, would disrupt the inhibitory effects of peripheral progesterone (study 2). Both studies were done in ovariectomized (OVX) and estradiol-treated OVX ewes. In study 1, no inhibitory effects of progesterone were observed during treatment in either area. In study 2, microimplants of RU486 into the ARC disrupted the negative-feedback actions of peripheral progesterone treatments on LH pulse frequency in both OVX and OVX+estradiol ewes. In contrast, microimplants of RU486 into the POA had no effect on the ability of systemic progesterone to inhibit LH pulse frequency. We thus conclude that the ARC is one important site of progesterone-negative feedback in the ewe. These data, which are the first evidence on the neural sites in which progesterone inhibits GnRH pulse frequency in any species, are consistent with the hypothesis that ARC dynorphin neurons mediate this action of progesterone.

Endocrinological actions of Unkei-to, a herbal medicine, and its clinical usefulness in anovulatory and/or infertile women

Kampo medicine (Chinese herbal medicine) has been reported to be effective in the treatment of pituitary-ovarian dysfunction in young women and in the treatment of undefined symptoms in perimenopausal women. It has been considered that both the diagnosis and treatment of ovulatory failure in adolescent girls or young women are necessary for the sake of future fertile capacity. However, treatment for the above patients is not easy as steroid hormones and strong stimulators of ovulation should not be recommended because of the several side-effects it causes. Furthermore, young women, especially teenagers, seem to be reluctant to visit gynecology clinics. A number of herbal medicines have been used for many centuries in China and Japan for the treatment of menstrual disorders and infertility. In general, the traditional Chinese herbal prescriptions are rather inexpensive and safe with little side-effects, and have properties for normalizing biological balances. Unkei-to is known to stimulate the synthesis and release of gonadotropins in the rat pituitary. In humans, Unkei-to is known to be effective in various menstrual disorders, abnormal uterine bleeding, and infertility. In the treatment of ovulatory failure, recent dynamic studies have revealed the mechanism by which Unkei-to stimulates the diencephalon-pituitary-ovarian axis in humans. In this paper, we critically review the clinical data available (to date) in order to assess the efficacy of Unkei-to in inducing ovulation in several types of ovulatory disturbances. (Reprod Med Biol 2003; 2: 45-61).