Endocrine Abstracts

Introduction: Pituitary and adrenal Cushing’s may be managed by pharmacological-inhibition of adrenal steroidogenesis, using metyrapone and/or ketoconazole. Assessment of biochemical control is challenging owing to cross-reactivity in immunoassays (e.g. cortisol and 11-deoxycortisol) leading to over/under-treatment. Off-target effects can also result, e.g. hyperandrogenism/mineralocorticoid hypertension (increased 11-deoxycorticosterone/DOC). LC-MS/MS analysis is free from cross-reactivity and allows quantification of multiple steroids.

Aim: Evaluate the utility of an LC-MS/MS method quantifying 13 steroids in medically-managed Cushing’s.

Methods: Eighty-one day curves (24 cases) were evaluated by LC-MS/MS and Centaur XP cortisol immunoassay. Thirteen had pituitary-disease (metyrapone±ketoconazole treatment) and 11 had adrenal-disease (metyrapone-only).

Results: In the metyrapone-only groups, pituitary-disease received a larger dose than adrenal-disease (1500 vs 750 mg/d, P=0.0004). Steroid concentrations were similar between pituitary/adrenal groups, except 11-deoxycortisol (80.6 vs 41.1 nmol/l, P=0.04), androstenedione (16.4 vs 6.6 nmol/l, P=0.001) and DHEAS (4.7 vs 0.6 μmol/l, P≤0.0001). In pituitary-disease, metyrapone dose positively correlated with 11-deoxycortisol (rs=0.53, P=0.01). In adrenal-disease, dose positively correlated with 11-deoxycortisol (rs=0.77), DOC (rs=0.59), 17-hydroxyprogesterone (rs=0.56) and androstenedione (rs=0.42, all P≤0.005) and negatively with cortisol (rs=−0.45, P=0.02). Cortisol method agreement differed: pituitary-disease LC-MS/MS=0.28 immunoassay +101.1 nmol/l and adrenal-disease LC-MS/MS=0.82 immunoassay ±8.7 nmol/l. Pituitary-disease treated with metyrapone and ketoconazole had higher 11-deoxycortisol (P=0.0003), 17-hydroxyprogesterone (P=0.0006) and DOC (P=<0.0001) than those treated with metyrapone-only. LC-MS/MS cortisol was lower in the dual therapy group (128 vs 205 nmol/l, P=0.01) but relatively higher by immunoassay (350 vs 232 nmol/l, NS). Cortisol method agreement in the metyrapone±ketoconazole group: LC-MS/MS=0.62 immunoassay±32.1 nmol/l. Seven/fourteen females demonstrated biochemical hyperandrogenism [increased testosterone/androstenedione (n=5), androstenedione-only (n=2)]. Across all day curves, those with highest DOC had relatively lower potassium concentration.

Conclusions: Marked differences in steroidogenesis were observed in pituitary vs adrenal Cushing’s. Unpredictable cross-reactivity in cortisol immunoassays mandates LC-MS/MS use in monitoring. Additionally, LC-MS/MS offers quantification of off-target steroidogenesis effects which may be clinically relevant.