Luteinizing hormone

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 Leutinizing Hormone

Leutinizing hormone (LH) is a glycoprotein hormone produced and secreted by the anterior pituitary gland . This is in response to the Growth hormone-releasing hormone (GHRH) secreted by the hypothalamus . It is an essential hormone in regulating the female ovarian cycle and stimulates the production of tesosterone in males . Therefore the target tissues of LH are Gonads. LH works in synergy with Follicle stimulating hormone (FSH) in both males and females.

Ovarian Cycle

Follicular phase
At the folicular phase, the loss of progesterone and higher oestrogen increases frequency of GHRH secretion pulses from hypothalamus . The LH to FSH secretion ratio increases. the decrease in concentration of FSH results in follicular atresia (apoptosis), leaving the dominant follicle. This dominant follicle produces and secretes oestrogen. With Oestrogen level at >200pg/ml, a surge of LH is induced. this surge of LH is enhanced by Prgesterone, in which triggers the Oocyte to complete meiosis 1 and ovulation.
Luteal phase
remnants from the follicle from the ovary form the corpus luteum this formation takes approximately 14 days to form. high levels in Progesterone inhibits and negatively feedbacks oestrogen, thus decreasing levels of FSH and LH.
If no fertilisation occurs following ovulation, then the corpus luteum degenerates to corpus albican. The level Oestrogen and Progesterone deplete allowing FSH and LH to rise. This release of negative feedback and the increase of FSH allows the recruitment of a crop of antral follicles to grow. Therefore iniating the start of anothe rround of the Ovarian cycle.

If fertilisation does occur, the placenta from embryo formation releases human chorionic gonadotropin which allows the corpus kluteum to stay.

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