Activity
GnRH activity is very low during childhood, and is activated at puberty. During the reproductive years, pulse activity is critical for successful reproductive function as controlled by feedback loops. However, once a pregnancy is established, GnRH activity is not required. Pulsatile activity can be disrupted by hypothalamic-pituitary disease, either dysfunction (i.e., hypothalamic suppression) or organic lesions (trauma, tumor). Elevated prolactin levels decrease GnRH activity. In contrast, hyperinsulinemia increases pulse activity leading to disorderly LH and FSH activity, as seen in polycystic ovary syndrome (PCOS). GnRH formation is congenitally absent in Kallmann syndrome.
The GnRH neurons are regulated by many different afferent neurons, using several different transmitters (including norepinephrine, GABA, glutamate). For instance, dopamine appears to stimulate LH release (through GnRH) in estrogen-progesterone-primed females; dopamine may inhibit LH release in ovariectomized females. Kisspeptin appears to be an important regulator of GnRH release. GnRH release can also be regulated by estrogen. It has been reported that there are kisspeptin-producing neurons that also express estrogen receptor alpha.
Read more about this topic: Gonadotropin-releasing Hormone
Famous quotes containing the word activity:
“Amour is the one human activity of any importance in which laughter and pleasure preponderate, if ever so slightly, over misery and pain.”
—Aldous Huxley (1894–1963)
“Play for young children is not recreation activity,... It is not leisure-time activity nor escape activity.... Play is thinking time for young children. It is language time. Problem-solving time. It is memory time, planning time, investigating time. It is organization-of-ideas time, when the young child uses his mind and body and his social skills and all his powers in response to the stimuli he has met.”
—James L. Hymes, Jr. (20th century)
“Life is a series of diminishments. Each cessation of an activity either from choice or some other variety of infirmity is a death, a putting to final rest. Each loss, of friend or precious enemy, can be equated with the closing off of a room containing blocks of nerves ... and soon after the closing off the nerves atrophy and that part of oneself, in essence, drops away. The self is lightened, is held on earth by a gram less of mass and will.”
—Coleman Dowell (1925–1985)