Co-administration of 5α-reductase Inhibitors Worsens the Adverse Metabolic Effects of Prescribed Glucocorticoids

Abstract

Context Glucocorticoids (GC) are commonly prescribed, but their use is associated with adverse metabolic effects. 5a-reductase inhibitors (5aRI) are also frequently prescribed, mainly to inhibit testosterone conversion to dihydrotestosterone. However, they also prevent the inactivation of GCs. Objective We hypothesised that 5aRIs may worsen the adverse effects of GCs. Design Prospective, randomised study. Patients 19 healthy male volunteers (age; 45±2 years, BMI; 27.1±0.7kg/m²). Interventions Participants underwent metabolic assessments; 2-step hyperinsulinemic, euglycemic clamp incorporating stable-isotopes, adipose tissue microdialysis and biopsy. Participants were then randomised to either prednisolone (10mg daily) or prednisolone (10mg daily) plus a 5aRI (finasteride 5mg daily or dutasteride 0.5mg daily) for 7 days; metabolic assessments were then repeated. Main Outcome Measures Ra glucose, glucose utilization (M-value), glucose oxidation, non-esterified fatty acids (NEFA) levels. Results Co-administration of prednisolone with a 5aRI increased circulating prednisolone levels (482±96 vs. 761±57nmol/L, p=0.029). Prednisolone alone did not alter Ra glucose (2.55±0.34 vs 2.62±0.19mg/kg/min, p=0.86), M-value (3.2±0.5 vs 2.7±0.7mg/kg/min, p=0.37), or glucose oxidation (0.042±0.007 vs 0.040±0.004mmol/hr/kg/min, p=0.79). However, co-administration with a 5aRI increased Ra glucose (2.67±0.16 vs. 3.05±0.18mg/kg/min, pvs. 2.6±0.4mg/kg/min, pvs. 0.036±0.002mmol/hr/kg, pvs. 36.8±14.3μmol/L, p=0.81), unless co-administered with a 5aRI (49.8±8.6 vs. 88.5±13.5μmol/L, p<0.01). Conclusions We have demonstrated that 5aRIs exacerbate the adverse effects of prednisolone. This study has significant translational implications, including the need to consider GC dose adjustments, but also the necessity for increased vigilance for the development of adverse effects.