We thank Dr Pecori Giraldi and colleagues for their letter concerning caution during the use of desmopressin in inferior petrosal sinus sampling (IPSS). The authors suggest that, because of the hypercoagulable state that characterizes Cushing's disease, desmopressin may not be safe since it has been shown to increase the level of von Willebrand factor and could therefore lead to platelet adhesion and cause thromboembolism. The authors point to their own published work suggesting this effect.1 In their paper, the authors show that, as well as von Willebrand factor, the levels of tissue plasminogen activator also increase, probably to achieve a balance by activating fibrinolytic pathways. Therefore, the increased risk of thromboembolic events in patients with Cushing's disease in the context of desmopressin administration is a theoretical consideration.

Thromboembolism is a rare complication of bilateral IPSS and, when reported, has been linked to lack of prophylaxis with intravenous heparin.2 ,3 In our practice we routinely heparinize patients undergoing bilateral IPSS, whether they receive corticotropin-releasing hormone (CRH) or desmopressin to stimulate the pituitary.4 The case series previously reported in which desmopressin rather than CRH was used did not indicate an increased risk of thromboembolic events.5–8 As the increased risk of thromboembolism is only a theoretical consideration, we can only use the available clinical data. Because the sensitivity of bilateral IPSS is significantly increased by the use of CRH or desmopressin, the benefits of using desmopressin appear at this point to outweigh the theoretical risks. One possible positive outcome of the CRH shortage is that more data will be accumulated to determine whether there are unexpected negative effects of using desmopressin.