The luteinizing hormone-releasing hormone pulse generator in men: abnormalities and clinical management

Article Abstract:

The gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), are secreted by the pituitary gland and stimulate the sex organs (gonads) to produce eggs or sperm. Their secretion is controlled by luteinizing hormone-releasing hormone (LHRH, also called gonadotropin-releasing hormone or GnRH), manufactured in the hypothalamus (a part of the brain) and secreted in a pulsatile fashion; thus, the release of LH into the blood also occurs in a pulsatile fashion. Part 2 of the November 1990 issue of the American Journal of Obstetrics and Gynecology presents papers from a symposium devoted to pulsatile GnRH, a method of hormone delivery that makes it possible to treat a variety of clinical disorders associated with testicular dysfunction. Two such disorders, associated with defective LHRH pulse generation, are hypogonadotropic eunuchoidism (with no apparent LH pulses) or idiopathic hypogonadotropic hypogonadism and idiopathic oligozoospermia with elevated FSH levels (with greatly reduced LH pulse frequencies). The first of these is characterized by a failure to undergo puberty, low levels of blood testosterone, low or normal levels of gonadotropins, and no other pituitary abnormalities. Men with idiopathic oligozoospermia (lack of sperm in the semen, from no known cause) compose most of the approximately five percent of men who are infertile; in about one fifth of the cases, they have high levels of FSH relative to the levels of LH. Treatment for hypogonadotropic eunuchoidism differs, depending on whether the goal is pubertal development and sexual functioning, or fertility. In the former case, testosterone administration usually accomplishes virilization. In the latter case, pulsatile LHRH can normalize pituitary secretion of gonadotropins and lead to fertility. No treatment for idiopathic oligozoospermia has yet been found, but pulsatile LHRH can decrease the abnormally elevated blood FSH levels. However, sperm production does not improve. Pulsatile LHRH warrants further investigation as an option for this presently untreatable disorder. (Consumer Summary produced by Reliance Medical Information, Inc.)

Evaluation, Drug therapy, Drug delivery systems, Infertility, Male, Male infertility, Oligospermia

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The GnRH pulse generator

Article Abstract:

Gonadotropin (luteinizing hormone, LH) is a chemical secreted by the pituitary gland that stimulates the sex organs (gonads) to produce eggs or sperm; its secretion is controlled by gonadotropin-releasing hormone (GnRH or LHRH), manufactured in the hypothalamus (a part of the brain). Part 2 of the November 1990 issue of the American Journal of Obstetrics and Gynecology presents papers from a symposium devoted to pulsatile GnRH, a method of hormone delivery that makes it possible to treat a variety of clinical disorders associated with ovarian dysfunction. A review of the medical literature is presented concerning the events in the central nervous system that contribute to the pulsatile nature of GnRH secretion. Initial investigations were hampered by a failure to realize that fluctuations occur often, sometimes more than once each hour. The GnRH pulse generator seems to lie within the hypothalamus (a part of the brain) - specifically, within the region's arcuate nucleus. Experiments are described that were undertaken to measure the neural activity (firing of nerve cells) in the arcuate nucleus that preceded the appearance of a burst of LH (an LH pulse) in the circulation of animals whose ovaries had been removed because the LH pulse is much harder to detect when gonads are present. Volleys of neural activity were detected in such cases, and the region appears to be the GnRH pulse generator. The pharmacologic characteristics of these cells are discussed. The reason studies of normal monkeys could not detect LH pulses was that the mild stress of the experimental situation inhibited the GnRH pulse generator, a finding that led to the development of new recording methods in these animals. Other results suggested that the duration and frequency of the GnRH pulse generator may be independently controlled. Hypotheses regarding the control of the generator are briefly discussed. (Consumer Summary produced by Reliance Medical Information, Inc.)

Measurement, Luteinizing hormone, Endocrine gland diseases, Endocrine diseases

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Discovery of the hypothalamic gonadotropin-releasing hormone pulse generator and of its physiologic significance

Article Abstract:

An early study was designed to determine whether a circadian rhythm in the plasma levels of the peptide could be detected. The observations in a non-human primate helped in the treatment of infertility that was attributed to hypothalamic dysfunction and in suppression of inappropriate gonadotropin secretion.

United States, Science & research, Care and treatment, Research, Circadian rhythms, Gonadotropin, Gonadotropins, Infertility, Female, Female infertility

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