Leutinizing hormone (LH) is a glycoprotein hormone produced and secreted by the anterior pituitary gland. This is in response to theGrowth hormone-releasing hormone (GHRH) secreted by the hypothalamus. It is an essential hormone in regulating the female ovarian cycle and stimulates the production of testosterone 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 regulation
At the follicular 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 Progesterone, in which triggers the Oocyte to complete meiosis 1 and ovulation.
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 initiating the start of another round of the Ovarian cycle.
Regulation of testicular function
LH targets Leydig cells. These cells synthesise testosterone. Similarly to females, in males, the hypothalamus secretes GHRH which triggers the secretion of LH and FSH from the pituitary gland. testosterone then negatively feedbacks to the hypothalamus and pituitary gland and inhibits secretion of LH. This testosterone then results in differentiation of male sex tissue such as the scotum.
- ↑ Neal J. How the Endocrine system works.2nd ed. West Sussex: John Wiley and Sons;2016. 129.
- ↑ White AW, Porterfield SP. Endocrine and reproductive physiology. 4th ed. Philadelphia: Elsevier Mosby; 2007. 109p
- ↑ O'Neil R, Murphy R. Endocrinology crash course. 4th ed. Philadelphia: Elsevier Mosby; 2012. 109
- ↑ White AW, Porterfield SP. Endocrine and reproductive physiology. 4th ed. Philadelphia: Elsevier Mosby; 2007. 227p
- ↑ White AW, Porterfield SP. Endocrine and reproductive physiology. 4th ed. Philadelphia: Elsevier Mosby; 2007. 224p
- ↑ Neal J. How the endocrine system works. 2nd ed. West Sussex: John Wiley andsons; 2016. 93p
- ↑ Norman AW, Henry HL. Hormones. 3rd ed. Oxford: Elsevier;2015. 266p