Neuroendocrine-ovarian axis (HPO axis)

The neuroendocrine-ovarian axis, also known as the hypothalamic-pituitary-ovarian (HPO) axis, is a complex physiological system that regulates female reproductive function and hormonal balance (StatPearls, 2023). It involves the pulsatile release of gonadotropin-releasing hormone (GnRH) from the hypothalamus, which stimulates the anterior pituitary to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH) (NIH, 2022). These gonadotropins then act on the ovaries to promote follicular development, ovulation, and the production of sex steroids like estrogen and progesterone (PubMed, 2021). This system is governed by intricate positive and negative feedback loops that ensure the proper timing of the menstrual cycle. Dysregulation of this axis is central to various clinical conditions, including infertility, polycystic ovary syndrome (PCOS), and endometriosis (Endocrine Reviews, 2018). Pharmacological intervention often targets specific receptors within this axis, such as the GnRH receptor or gonadotropin receptors, to manage reproductive disorders or provide contraception (Journal of Clinical Endocrinology & Metabolism, 2020).

Other names

Hypothalamic-pituitary-ovarian axisHypothalamic-pituitary-gonadal axisHPG axisNeuroendocrine-gonadal axis

Drugs targeting this axis act by modulating the feedback loops between the hypothalamus, pituitary, and ovaries. This is typically achieved through the agonism or antagonism of the GnRH receptor to suppress or stimulate the release of FSH and LH, or through the direct administration of gonadotropins to stimulate ovarian follicles (StatPearls, 2023; NIH, 2022).