It is often thought that hormones are "annoying" and cause emotional instability and the importance is often overlooked. Let's have a more detailed look at the endocrinology of the female reproductive system. The hormonal axis plays an important role in reproductive health and fertility.
Once puberty has been reached, the reproductive system kicks into gear and sexual maturity is reached in the individual's body. The endocrinology and release of hormones in the female reproductive system is basically achieved through three major centers: the hypothalamus, anterior pituitary and the ovaries.
The hypothalamus is a small region of the brain located at the base with close proximity to the pituitary. It is comprised of three main regions. Our focus will be the anterior region or supraoptic region which is responsible for the secretion of various hormones. Our hormone of interest in gonadotrophin-releasing hormone (GnRH) which acts on the anterior pituitary.
The pituitary gland is a small gland underneath the brain which is attached to the hypothalamus. It is comprised of an anterior and posterior region. It is often referred to as the "master gland" because of its responsibility of producing many hormones in the body. Our hormones of interest in the female are the gonadotrophes: luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
At the level of the ovaries, FSH causes stimulation and the growth of follicles. This also induces the production of estrogen. The rise in estrogen, past a threshold value, feeds back to the pituitary to reduce the production of FSH. Estrogen has more of an effect on FSH secretion than LH secretion. The developing follicles also produce the hormone inhibin which inhibits production of FSH but not LH. At this point, LH begins to rise. Once estrogen has reached another threshold, it causes and increase in LH production. The rise in LH is known as the "LH surge" which cause ovulation of the follicle occurs approximately 36 hours after the surge. The remainder of the follicle in the ovary forms the corpus luteum which secretes progesterone necessary for the maintenance of pregnancy. If pregnancy occurs, the corpus luteum continues the production of progesterone until the placenta takes over. The high levels of progesterone, estrogen and inhibin decrease FSH and LH production. If pregnancy does not occur, progesterone levels decrease and another cycle begins.
This was a brief overview of the main hormones involved in an ovulatory cycle. If any of these hormones are not functioning optimally, there may be fertility issues as a result. Therefore, in fertility investigations, hormonal blood work in a cycle can give a better understanding of how the reproductive system is functioning. It can provide hints as to where the problem may lie.
