Activity
In both males and females, LH is essential for reproduction.
- In females, LH supports theca cells in the ovaries that provide androgens and hormonal precursors for estradiol production. At the time of menstruation, FSH initiates follicular growth, specifically affecting granulosa cells. With the rise in estrogens, LH receptors are also expressed on the maturing follicle, which causes it to produce more estradiol. Eventually, when the follicle has fully matured, a spike in estrogen production by the follicle stimulates a positive feedback loop in the hypothalamus that stimulates the release of LH from the anterior pituitary. This increase in LH production only lasts for 24 to 48 hours. This "LH surge" triggers ovulation, thereby not only releasing the egg from the follicle, but also initiating the conversion of the residual follicle into a corpus luteum that, in turn, produces progesterone to prepare the endometrium for a possible implantation. LH is necessary to maintain luteal function for the first two weeks of the menstrual cycle. If pregnancy occurs, LH levels will decrease, and luteal function will instead be maintained by the action of HCG (a hormone very similar to LH but secreted from the new placenta).
- In the male, LH acts upon the Leydig cells of the testis and is responsible for the production of testosterone, an androgen that exerts both endocrine activity and intratesticular activity on spermatogenesis.
The release of LH at the pituitary gland is controlled by pulses of gonadotropin-releasing hormone (GnRH) from the hypothalamus. Those pulses, in turn, are subject to the estrogen feedback from the gonads.
Read more about this topic: Luteinizing Hormone
Famous quotes containing the word activity:
“What have we achieved in mowing down mountain ranges, harnessing the energy of mighty rivers, or moving whole populations about like chess pieces, if we ourselves remain the same restless, miserable, frustrated creatures we were before? To call such activity progress is utter delusion. We may succeed in altering the face of the earth until it is unrecognizable even to the Creator, but if we are unaffected wherein lies the meaning?”
—Henry Miller (1891–1980)
“A worm is as good a traveler as a grasshopper or a cricket, and a much wiser settler. With all their activity these do not hop away from drought nor forward to summer. We do not avoid evil by fleeing before it, but by rising above or diving below its plane; as the worm escapes drought and frost by boring a few inches deeper.”
—Henry David Thoreau (1817–1862)
“In literary circles, the men of trust and consideration, bookmakers, editors, university deans and professors, bishops, too, were by no means men of the largest literary talent, but usually of a low and ordinary intellectuality, with a sort of mercantile activity and working talent. Indifferent hacks and mediocrities tower, by pushing their forces to a lucrative point, or by working power, over multitudes of superior men, in Old as in New England.”
—Ralph Waldo Emerson (1803–1882)