Hypothalamic-pituitary-gonadal axis: Difference between revisions
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== HPG Axis in Males == | == HPG Axis in Males == | ||
In males, the HPG axis | In males, the HPG axis is mainly involved in the regulation of the production of testosterone and the process of spermatogenesis. LH is involved in the synthesis of testosterone via binding to the interstitial cells of the testes while FSH is involved in production of spermatozoa (spermatogenesis). | ||
[[File:Hypothalamus pituitary testicles axis.png|thumb|e.g. 100px|thumb|Hypothalamic-pituitary-testicular axis]] | |||
[[File:Testosterone.PNG|thumb|e.g. 100px|thumb|Chemical Structure of Testosterone]] | [[File:Testosterone.PNG|thumb|e.g. 100px|thumb|Chemical Structure of Testosterone]] | ||
Revision as of 20:32, 22 January 2014
Introduction
The hypothalamic-pituitary-gonadal axis (HPG axis) alludes to the connection between the hypothalamus, pituitary gland, and gonads. It is an important control mechanism mainly involved in the development and regulation of the reproductive system and immune system. It is also involved in the aging process. As with other hypothalamic-pituitary related axes, regulation is through a negative feedback loop.
Regulation & Function
The hypothalamus produces a hormone called gonadotropin-releasing hormone (GnRH). When GnRH is released, it travels along the hypophyseal portal system and binds to secretory cells of the anterior pituitary (adenohypophysis). Binding of GnRH stimulates these cells to produce luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which are then secreted into the bloodstream. From here, LH and FSH go on to produce different effects in both sexes.
HPG Axis in Females
In females, the HPG axis is mainly involved in the regulation of the menstrual and ovarian cycle. Once the anterior pituitary releases LH and FSH into the bloodstream, these hormones signal the ovaries to produce estrogen and inhibin. Both estrogen and inhibin possess properties that can suppress the production of GnRH. Estrogen directly inhibits GnRH production via a negative feedback loop. Inhibin indirectly inhibits GnRH production by inhibiting the protein complex activin.
HPG Axis in Males
In males, the HPG axis is mainly involved in the regulation of the production of testosterone and the process of spermatogenesis. LH is involved in the synthesis of testosterone via binding to the interstitial cells of the testes while FSH is involved in production of spermatozoa (spermatogenesis).
Links
Related articles
References
1. Millar, R.P., Lu, Z.L., Pawson, A.J., Flanagan, C.A., Morgan, K., & Maudsley, S.R. (2004). Gonadotropin-releasing hormone receptors. Endocrine Reviews, 25, 235-75.
2. Peper, J.S., Brouwer, R.M., van Leeuwen, M., Schnack, H.G., Boomsma, D.I., Kahn, R.S., & Hulshoff Pol, H.E. (2010). HPG-axis hormones during puberty: A study on the association with hypothalamic and pituitary volumes. Psychoneuroendocrinology, 35(1), 133-140.
