Hormones are fascinating indeed. The function of each is so intricate which makes it even more unfathomable as to how perfectly they function in concert with each other in a normal self. Despite exposing this self to food, drugs and other chemicals. Since I am majoring in reproductive science I spend my time reading mostly related topics. Hence, I will be writing about the hormones respective to that.

It is known that GnRH is secreted by the Hypothalamus which in turn stimulates the master gland, the pituitary to release the gonadotropins (a.k.a sex hormones) which then proceeds further in performing its various functions. How simple. Little did I know that it takes so much more than this. So, as I started reading more about GnRH I was introduced to several other hormones that also help in its secretion and inhibition.

Kisspeptin:

This is a protein product of KISS1 gene located on chromosome 1q32.1. This protein is of prime importance as it stimulates the production of GnRH during puberty. The functioning of the gene in production of this protein begins on around the time of puberty. Therefore, if activated earlier may result in precocious puberty. It is said that kisspeptin works with G protein couple receptor (GPR54) present of the GnRH neurons.

At the time of puberty, GnRH is released in a pulsatile manner. This is because, peptide kisspeptin works full time and continuously stimulates the GPR54 present on the GnRH neuronal population. As a result of which there is a desensitization of the receptor and fails to transmit signals to the anterior pituitary. Therefore there is a sharp decline in the levels of the gonadotropins (LH, FSH) after which again the GPR54 receptor is sensitive for kisspeptin.

Metabolic hormones:

Kisspeptin is also involved in the regulation of the reproductive axis (hypothalamo-pituitary-gonadal axis) by signals from metabolic factors or hormones like, leptin and ghrelin.

Leptin is a hormone produced by fat cells (adipocytes). It is a satiety hormone and inhibits hunger. Apart from this main function, it also stimulates the kisspeptin neurons which in turn stimulates the production of GnRH. Therefore, fat stores in the body also have an influence in stimulation of reproductive hormones. This also explains why obese children attain puberty at an early age than normal. Because, the fat stores in the body activate kisspeptin way before it has to be activated. And, during starvation there is less secretion of leptin therefore, reproductive hormones are not stimulated.

On the contrary, ghrelin is another metabolic hormone that signals energy deficiency. Simply put, it induces hunger. Increased levels of which indicate starvation which inhibits gonadotropin secretion.

This entire relation between reproduction and metabolic hormones have evolutionary basis. Most animals do not have access to food at all times. They either over eat and fill their stomachs or starve for days. While starving, they cannot afford to reproduce as reproduction is an energy draining process and may threaten survival. Therefore, at such times the body has to prioritize and preserve energy for other physiological processes essential for survival. In such situations, reproduction is completely dispensable.

This was the most interesting of reads recently. However there is more to metabolic control of reproduction. Which I will probably be writing later. That’s all for now.