The low dose dexamethasone suppression test (LDDT) is used routinely to exclude Cushings. This test can also be used to exclude androgen secreting tumours in females with elevated testosterone levels through normalisation of, or >40% suppression of serum levels.
We have audited the use of the LDDT to assess its value in investigating women with raised androgens, to ascertain whether it reduced the need for other investigations and to identify any problems encountered in performing the test.
Method: We reviewed the notes and results of all female patients referred to the clinical investigation unit for LDDT investigation of elevated androgen levels.
Results: 26/34 patients suppressed their testosterone levels by >40%. 6/34 suppressed by <40%, all of whom underwent further investigation. 50% were found to have a tumourous cause for the hyperandrogenism.
1/26 patient suppressed by 43% but her testosterone levels remained elevated (5.3 nmol/l). A repeat LDDT resulted in 33% suppression. Further investigation is underway to rule out a tumourous cause in this case.
Two patients having the LDDT for the investigation of hyperandrogenism were found to have non-suppressible cortisol. Cushings syndrome has subsequently been confirmed in both cases. No adverse events were encountered in any patient.
Summary: The LDDT is a simple, well tolerated test. It has allowed confident exclusion of tumourous causes of hyperandrogenism, and dramatically reduced the need for further complex investigation. In the light of 1/34 significant anomalous result, we propose that a normal result requires suppression of testosterone levels by both >40% AND into the normal range in future.