A 58-year old women with a complex medical history (renal failure with 3rd transplant, post-Hep C cirrhosis, steroid-induced diabetes, hyperparathyroidism, uterine fibroid) presented with persistent, highly elevated (male range) serum testosterone concentrations with some limited virilisation. Serum testosterone was 15.7-31.0 nmol/L (normal female <1.8 nmol/L) on multiple occasions, confirmed by two different LCMS methods, menopausal serum LH (59-69 IU/L), FSH (62-64 IU/L), SHBG (76-96 nmol/L) and GFR 64 ml/min. No mass lesions in adrenal (ultrasound, MRI) or ovaries (MRI, CT). Adrenal and ovarian vein cannulation identified strong gradients in left ovarian vein (10-30 fold vs peripheral serum in 17OHP4, 17 OHP5, A4, T, DHEA from 15 steroid LCMS profile), no adrenal vein gradients but right ovarian vein unable to be cannulated. A second ovarian vein cannulation confirmed the first study (18-fold gradient T, >60-fold gradient 17OHP4, 17OHP5, A4, DHEA) but right ovarian vein cannulation again failed. Presumptive diagnosis was ovarian hyperthecosis with bilateral ovarian steroidogenesis of a wide range of precursors and metabolites of bioactive steroids driven by high (menopausal) serum gonadotrophins. The diagnosis was confirmed by a single dose of a pure GnRH antagonist (80 mg degarelix, Ferring) producing a complete and rapid (within 24 hr) suppression of all ovarian steroids as well as serum LH and FSH lasting for at least 4 weeks. Transient side-effects were injection site pain (2 days) and severe flushing in 2nd to 3rd week post-injection, alleviated by an estradiol patch but wearing off in 4th week. This case illustrates the utility (and limitations) of ovarian vein cannulation coupled with steroid LCMS profiling for diagnosis of severe hyperandrogenism in a postmenopausal woman without adrenal or ovarian tumour on imaging. This is the first reported use of a pure GnRH antagonist for diagnosis and treatment of ovarian hyperthecosis.