Severe ovarian hyperstimulation syndrome after letrozole-gonadotropin stimulation: a case report

Abstract

Ovarian hyperstimulation syndrome (OHSS) results from an exaggerated response to ovulation induction, characterized by a fluid shift from the intravascular space to third space compartments. The incidence of moderate OHSS is approximately 3–6% and severe OHSS occurs in 0.1–3% of treatment cycles [1, 2]. A number of causal mechanisms have been investigated, involving estradiol (E2), human chorionic gonadotropin (hCG), and vascular endothelial growth factor (VEGF). A strong association between E2 concentrations and risk for developing OHSS has been observed consistently [3]. A growing awareness and interest in treatments aimed at fertility preservation (FP) has led many women to pursue urgent oocyte or embryo cryopreservation. Those with estrogen-sensitive cancers often receive adjunctive treatment with letrozole, in efforts to limit exposure to elevated estrogen concentrations that typically result from exogenous gonadotropin stimulation; letrozole inhibits estrogen production by binding competitively to the cytochrome P450 component of the aromatase enzyme. Combination stimulation regimens yield results comparable to those achieved with standard gonadotropin stimulation protocols, but are associated with significantly lower E2 levels [4]. The risk of OHSS for women receiving adjunctive treatment with letrozole generally is considered low, because E2 levels are markedly lower than in cycles stimulated with gonadotropins alone. In fact, no cases of severe OHSS have been reported in a patient receiving combined treatment with letrozole and gonadotropins. Here, we report a case of severe OHSS arising in a woman with breast cancer after stimulation with exogenous gonadotropins, despite treatment with letrozole and having only moderately elevated E2 concentrations.