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:
“Moderation is the feebleness and sloth of the soul, whereas ambition is the warmth and activity of it.”
—François, Duc De La Rochefoucauld (1613–1680)
“To play is nothing but the imitative substitution of a pleasurable, superfluous and voluntary action for a serious, necessary, imperative and difficult one. At the cradle of play as well as of artistic activity there stood leisure, tedium entailed by increased spiritual mobility, a horror vacui, the need of letting forms no longer imprisoned move freely, of filling empty time with sequences of notes, empty space with sequences of form.”
—Max J. Friedländer (1867–1958)
“In communist society, where nobody has one exclusive sphere of activity but each can become accomplished in any branch he wishes, society regulates the general production and thus makes it possible for me to do one thing today and another tomorrow, to hunt in the morning, fish in the afternoon, rear cattle in the evening, criticize after dinner, just as I have a mind, without ever becoming hunter, fisherman, shepherd or critic.”
—Karl Marx (1818–1883)