Hypothalamic-pituitary-ovarian axis (HPO axis) (HPO axis)

The hypothalamic-pituitary-ovarian (HPO) axis is a fundamental neuroendocrine system responsible for the regulation of the female reproductive cycle and the maintenance of hormonal homeostasis (StatPearls, 2023). The axis operates through a hierarchical signaling cascade starting with the pulsatile secretion of Gonadotropin-releasing hormone (GnRH) from the hypothalamus, which triggers the release of Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH) from the anterior pituitary (NIH, 2022). These gonadotropins stimulate the ovaries to undergo folliculogenesis and produce essential steroid hormones, primarily estradiol and progesterone (Endocrine Society, 2023). These ovarian steroids exert both positive and negative feedback on the hypothalamus and pituitary to coordinate the menstrual cycle and ovulation. Clinical dysfunction of the HPO axis is associated with various reproductive disorders, including polycystic ovary syndrome (PCOS), functional hypothalamic amenorrhea, and infertility (PubMed, 2021). Therapeutic strategies targeting this axis include the use of GnRH agonists and antagonists, exogenous gonadotropins, and selective estrogen receptor modulators (SERMs) to manage conditions ranging from endometriosis to assisted reproduction (Journal of Clinical Endocrinology & Metabolism, 2020).

Other names

Neuroendocrine-ovarian axisHypothalamic-pituitary-gonadal axis (female)HPO axisHypothalamic-pituitary-ovarian system

GnRH receptor agonism and antagonism, FSH and LH receptor stimulation, and selective estrogen receptor modulation (SERM) to influence feedback loops.