Clinical meaning
Ovarian hyperstimulation syndrome (OHSS) is a potentially life-threatening iatrogenic complication of controlled ovarian stimulation used in assisted reproductive technologies such as in vitro fertilization (IVF). The condition occurs when the ovaries respond excessively to gonadotropin hormones (follicle-stimulating hormone and human chorionic gonadotropin), leading to the development of multiple enlarged follicles and markedly elevated estradiol levels. The pathophysiology centers on massive vascular endothelial growth factor (VEGF) release from the hyperstimulated ovarian tissue. VEGF dramatically increases capillary permeability throughout the body, causing a systemic capillary leak syndrome. This increased vascular permeability causes protein-rich fluid to shift from the intravascular space into the interstitial and third spaces (peritoneal cavity, pleural space, and pericardial space). The resulting third-spacing of fluid leads to two simultaneous and paradoxical problems: intravascular volume depletion (hemoconcentration, hypotension, tachycardia, oliguria) and extravascular fluid accumulation (ascites, pleural effusions, peripheral edema). The ovaries become massively enlarged, sometimes reaching 10-12 centimeters in diameter (normal ovary is approximately 3 centimeters), and are at high risk for torsion (twisting on the ovarian pedicle, which compromises blood supply) and rupture. Hemoconcentration from intravascular fluid loss increases...