The hypothalamic pituitary gonadal axis, also known as HPG axis, reports to the effects and tendencies of the hypothalamus, pituitary gland, and gonads, as though these endocrine glands were a whole. This is done because it is more advantageous and practical for endocrinologists and physiologists to see them as one connected system, seeing how these glands often act together. The main function of the hypothalamic pituitary gonadal axis is that it plays an important role in the development and equilibrium of certain systems in our bodies, like the immune system, or the reproductive system. For example, any hormonal fluctuation is felt by the HPG axis, and each gland will produce changed values of hormones each, leading to certain imbalances and secondary effects in the body.
In animals, the hypothalamic pituitary gonadal axis is directly connected to development, reproduction and aging. As for each gland separately, they have the following functions: the hypothalamus is responsible with producing the gonadotropin-releasing hormone, the gonads produce testosterone and estrogen and, finally, part of the pituitary gland is known for producing follicle-stimulating hormone and luteinizing hormone. In what follows we’ll explain the exact manifestations of the hypothalamic pituitary gonadal axis and its effects in the body.
It all starts with the hypothalamus, which is found in the brain, and secretes the above-mentioned hormone. The gonadotropin-releasing hormone goes all the way to the pituitary gland and attaches itself to receptors of the secretory cells, which in turn produce the hormones mentioned above, which are luteinizing hormone and follicle-stimulation hormone; these hormones travel through the blood stream and are a major part of communication with the gonads. With females, these two hormones act to spark off the ovaries which then start producing estrogen and inhibin, and the menstrual and ovarian cycles are regulated. Generally, all these hormones act in a very complex way, sometimes together, to balance certain functions in the body.
With males, for example, the luteinizing hormone incites the interstitial cells to produce testosterone and the follicle-stimulation hormone is important for spermatogenesis. A very important role that the hypothalamic pituitary gonadal axis has is that it is responsible with the normal functioning of the reproductive system. In females, it does that by controlling and regulating the ovarian and uterine cycles. In simpler terms, the axis creates an exchange of hormones in the body, which balance certain functions and prepare the uterus to receive the fertilized egg. Imbalances in the HPG axis can lead to secondary sex characteristics and ovulation disorders, but they can be treated.