Endocrine Abstracts

Introduction: Steroid profiling using liquid chromatography with tandem mass spectroscopy (LC:MS) has a low cost per sample and has the potential for high through-put processing. However, although this technology is becoming more widely used, little is known of the normal ranges of many less well studied steroid compounds as well as their response to a variety of physiological stimulants.

Methods: Volunteers were recruited to a randomised, double blind cross-over study and adhered to a standard salt diet for 3 days with salt loading (slow sodium tabs) or placebo. After 30 min recumbent rest, samples were obtained pre and post ACTH and angiotensin II infusions. Samples were extracted from plasma using Chem Elute cartridges (Varian, CA, USA) and injected into a C-18-A reversed phase HPLC column. Identification and quantification were accomplished by tandem mass spectrometry using Varian 1200L mass spectrometer.

Results: High and standard salt phases were confirmed by 24 h urinary sodium excretion and plasma renin concentrations (PRC). Mean (24 h Na, standard salt 97.1±39.5 mmol, high salt 199.8±64.6 mmol, P<0.001; PRC, standard salt phase 19.1±13.9 mIU/l, high salt phase 9.7±5.9 mIU/l, P<0.001). Aldosterone and its immediate precursor, 18-hydroxycorticosterone were stimulated by salt restriction and angiotensin II infusion. There was no difference in deoxycorticosterone or 18-hydroxydeoxycorticosterone following angiotensin II infusion. Cortisol, 11-deoxycortisol, corticosterone and cortisone concentrations were reduced following angiotensin II infusion. As expected, ACTH stimulated all measured corticosteroids compounds.

Conclusions: These data suggest that angiotensin II infusion is associated with a reduction in cortisol and its precursor steroid hormones. In addition, aldosterone synthase is likely to catalyse the 18-hydroxylation of corticosterone but not 18-hydroxylation of deoxycorticosterone. Steroid profiling by LC:MS can reveal a more comprehensive picture of the ‘steroid-ome’ leading to a greater understanding of the factors controlling the steroid pathway.

Declaration of funding: This work was supported by the Medical Research Council (F M, Clinical Training Fellowship G0601322; E D, J M C, R F, Programme Grant G0400874).