Role of hormonal and inflammatory alterations in obesity-related reproductive dysfunction at the level of the hypothalamic-pituitary-ovarian axis

Obesity-related reproductive dysfunction involves hormonal and inflammatory alterations that affect the hypothalamic-pituitary-ovarian (HPO) axis, which plays a critical role in female reproductive function. Here’s an overview of the role of hormonal and inflammatory changes in obesity-related reproductive dysfunction:

  1. Hormonal alterations:
  • Leptin resistance: Leptin, a hormone secreted by adipose tissue, regulates energy balance and reproductive function. In obesity, high levels of leptin can lead to leptin resistance, where the body becomes less responsive to the hormone’s signals. Leptin resistance disrupts the feedback loop between adipose tissue and the hypothalamus, affecting the regulation of gonadotropin-releasing hormone (GnRH) and subsequent gonadotropin secretion.
  • Insulin resistance and hyperinsulinemia: Obesity often coincides with insulin resistance, where the body’s cells become less responsive to insulin’s actions. Insulin resistance can lead to increased insulin levels in the blood (hyperinsulinemia), which may impact ovarian function. Insulin resistance can also influence the synthesis and metabolism of sex steroid hormones, such as estrogen and androgens, further disrupting the HPO axis.
  • Androgen excess: Obesity-related hormonal alterations can contribute to increased production of androgens (e.g., testosterone) by the ovaries and adrenal glands. Elevated androgen levels can disrupt normal ovarian function, inhibit follicular development, and contribute to conditions like polycystic ovary syndrome (PCOS).
  1. Inflammatory alterations:
  • Chronic low-grade inflammation: Obesity is associated with a state of chronic low-grade inflammation, characterized by elevated levels of pro-inflammatory cytokines and adipokines. These inflammatory factors can interfere with the functioning of the HPO axis.
  • Disruption of GnRH pulsatility: Inflammation can disrupt the pulsatile release of GnRH from the hypothalamus. GnRH pulsatility is crucial for the regulation of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) secretion from the pituitary gland, which are essential for follicular development and ovulation.
  • Altered ovarian function: Inflammatory cytokines can affect ovarian function by disrupting folliculogenesis, inhibiting the maturation of oocytes, and impairing ovulation.
  • Impaired steroidogenesis: Inflammatory alterations in obesity can interfere with the synthesis and metabolism of sex steroid hormones in the ovaries, leading to hormonal imbalances and fertility issues.

These hormonal and inflammatory alterations collectively contribute to obesity-related reproductive dysfunction by disrupting the normal functioning of the HPO axis. Understanding these mechanisms is crucial for developing interventions and treatment strategies targeting the underlying causes of infertility and reproductive challenges in obese individuals.