Schally, A. V., Kastin, A. J., & Arimura, A. (1972). The hypothalamus and reproduction. American journal of obstetrics and gynecology, 114(3), 423-442. https://doi.org/10.1016/0002-9378(72)90620-5
Schally AV, Kastin AJ, Arimura A. The hypothalamus and reproduction. Am J Obstet Gynecol. 1972;114(3):423-442. doi:10.1016/0002-9378(72)90620-5
Schally, Andrew V., et al. "The hypothalamus and reproduction." American journal of obstetrics and gynecology, vol. 114, no. 3, 1972, pp. 423-442.
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Abstract
This article has been designed to review recent developments in the field of hypothalamic hormones involved in the control of reproductive functions. A brief resume of early physiologic and anatomic studies was presented initially to give a better understanding of the concept of hypothalamic regulation of the release of gonadotropic hormones from the pituitary gland. Recently, an advance was achieved with the isolation from porcine hypothalami of a decapeptide which has both FSH-releasing hormone (FSH-RH) activity and LH-releasing hormone (LH-RH) activity. Its amino acid sequence was determined to be (pyro) gluhis-trp-ser-tyr-gly-leu-arg-pro-gly-NH2. The decapeptide corresponding to this structure was synthesized and shown to stimulate the release of LH and of FSH in laboratory and domestic animals and human beings. Natural and synthetic FSH-RH/LH-RH also stimulated the synthesis of both gonadotropins in tissue cultures of rat pituitaries in vitro. It was postulated that this decapeptide represents the hypothalamic hormone which regulates the release of both LH and FSH from the anterior pituitary gland. Complex effects of sex steroids on the release of LH and FSH were reviewed briefly. It was suggested that the over-all control of secretion of FSH and LH is most likely mediated by the interaction of hypothalamic FSHand LH-releasing hormone with sex steroids. Clinical studies performed with natural and synthetic LH-RH/FSH-RH were reviewed. These studies, particularly induction of ovulation, suggest that LH-RH should find practical application in the treatment of sterility. Subsequent synthesis of LH-RH/FSH-RH by several laboratories and drug houses should provide enough material for large-scale clinical evaluation of this hormone. Some comments were made concerning probable clinical use of LH-RH. Finally, some speculations were offered about the possibility of developing new birth control methods based on LH-RH/FSH-RH, its analogues, or its derivatives.
Substantial evidence now exists to indicate that the endogenous hypothalamic opioidergic mechanism(s) represents one of the important controlling systems for release of gonadotropin-releasing hormone. Modulations of frequency and amplitude of the secretory activity of gonadotropin-releasing hormone appears to be mediated through an inhibitory action of endogenous opioids, and the functional coupling of the opioidergic and gonadotropin-releasing hormone systems is an ovarian steroid-dependent event. There is also evidence to implicate suprahypothalamic mechanism(s) that enhance endogenous opioid inhibition of secretion of gonadotropin-releasing hormone. Although exogenous opioid peptides and their synthetic analogs consistently induce the secretion of prolactin, blockade of opioid receptors in humans by naloxone failed to elicit a decrement in the levels of prolactin under a variety of conditions. On the contrary, naloxone induced a remarkable increment in the secretion of prolactin via an increased frequency of pulsatile release which is synchronized with pulses of luteinizing hormone. These observations suggest that a common neuroendocrine mechanism is involved in the opioidergic control of the secretion of both luteinizing hormone and prolactin in women.
In rhesus monkeys with hypothalamic lesions (which appear to abolish the endogenous production of gonadotropin-releasing hormone), normal ovulatory mestrual cycles were reestablished by an unvarying, long-term replacement regimen consisting of one intravenous pulse of synthetic gonadotropic-releasing hormone per hour. This finding is in accord with the hypothesis that the pattern of pituitary gonadotropin secretion throughout the menstrual cycle (basal secretion interrupted, once every 28 days on the average, by a preovulatory surge) is not directed by alterations in hypothalamic gonadotropin-releasing hormone secretion but by the ebb and flow of ovarian estrogens acting directly on the pituitary gland.
The notion of an oscillator or signal generator in the central nervous system that controls the rhythmic release of GnRH and, thereby, the pulsatile secretion of the gonadotropic hormones, originated in the finding of strikingly abrupt and rhythmic fluctuations in the concentration of LH in the plasma of ovariectomized monkeys. These oscillations had a period of about one hour when blood samples were obtained at 10 to 20 minute intervals.I
These surprising observations were presaged by reports of seemingly random, major fluctuations in plasma gonadotropin concentrations in gonadectomized monkeys" and rats as well as in women.' In these earlier studies, the sampling intervals employed were never less than one hour and unable, therefore, to reveal the orderly, rhythmic events that occur with frequencies of one event per hour or more.
In the original study describing pulsatile LH secretion in ovariectomized monkeys the possibility was considered that the circhoral discharges of LH may be initiated by autoregulatory mechanisms involving long or short feedback loops, but the more likely view that these discharges were due to intermittent signals from the central nervous system unrelated to circulating LH levels that resulted in putative increments in GnRH release was favored. Nevertheless, the possible role of autoregulatory mechanisms in the control of pulsatile LH secretion was repeatedly considered,6 but finally laid to rest in the relatively recent past.7Conversely, the view that each pulse of LH released from the pituitary gland is the consequence of a bolus of GnRH secreted into the pituitary portal system has been unequivocally upheld by the demonstration of synchronous increments of GnRH assessed in the pituitary portal circulation and of LH measured in samples of peripheral blood obtained simultaneously.s, 9 In any case, the phenomenon of pulsatile gonadotropic hormone secretion was rapidly extended to most vertebrate species studied in this regard, including our own, and forms the basis of an increasingly voluminous, rapidly expanding literature.
Ovariectomized rhesus monkeys bearing hypothalamic lesions which had abolished endogenous LHRH production, as evidenced by a profound reduction in gonadotropin secretion, but in which LH and FSH secretion was reestablished by a chronic intermittent iv infusion of synthetic LHRH (1 microgram/min for 6 min every hour) were used to investigate the sites of the negative and positive feedback actions of estradiol in the control of gonadotropin secretion. The administration of estradiol to such animals, while continuing the LHRH replacement regimen, resulted in a decline in circulating LH and FSH levels, followed by an unambiguous discharge of these hormones. The time course of this biphasic pattern of gonadotropin secretion was remarkably similar to that observed in response to estradiol administration in otherwise intact ovariectomized animals. These results suggest that, in the rhesus monkey, estradiol can exert both its negative and positive feedback actions on gonadotropin secretion at the level of the pituitary gland.
PMID 4567509 4567509 DOI 10.1016/0002-9378(72)90620-5 10.1016/0002-9378(72)90620-5 Schally et al. 1972, Schally 1972
Cite this article
Schally, A. V., Kastin, A. J., & Arimura, A. (1972). The hypothalamus and reproduction. American journal of obstetrics and gynecology, 114(3), 423-442. https://doi.org/10.1016/0002-9378(72)90620-5
Schally AV, Kastin AJ, Arimura A. The hypothalamus and reproduction. Am J Obstet Gynecol. 1972;114(3):423-442. doi:10.1016/0002-9378(72)90620-5
Schally, Andrew V., et al. "The hypothalamus and reproduction." American journal of obstetrics and gynecology, vol. 114, no. 3, 1972, pp. 423-442.
