Reduction in daily hydrocortisone dose improves bone health in primary adrenal insufficiency.

Objective: Individuals with primary adrenal insufficiency (PAI) or congenital adrenal hyperplasia (CAH) receive life-long glucocorticoid (GC) replacement therapy. Current daily GC doses are still higher than the reported adrenal cortisol production rate. This GC excess could result in long-term morbidities such as osteoporosis. No prospective trials have investigated the long-term effect of GC dose changes in PAI and CAH patients.

Methods: This is a prospective and longitudinal study including 57 subjects with PAI (42 women) and 33 with CAH (21 women). Bone mineral density (BMD) was measured by dual energy X-ray absorptiometry at baseline and after 2 years. Subjects were divided into three groups (similar baseline characteristics) depending on changes in daily hydrocortisone equivalent dose (group 1: unchanged 25.2±8.2  mg (mean±S.D., n=50); group 2: increased 18.7±10.3 to 25.9±12.0  mg (n=13); group 3: decreased 30.8±8.5 to 21.4±7.2  mg (n=27)).

Results: Subjects in group 1 showed normal lumbar and femoral Z-scores which were unchanged over time. Group 2 subjects showed a significant decrease in femoral neck Z-scores over time (-0.15±1.1 to -0.37±1.0 (P<0.05)), whereas group 3 subjects showed a significant increase in lumbar spine and hip Z-scores (L1-L4: -0.93±1.2 to -0.65±1.5 (P<0.05); total hip: -0.40±1.0 to -0.28±1.0 (P<0.05)). No changes in BMI over time were seen within any group. Reduction in GC dose did not increase the risk of adrenal crisis.

Conclusion: This study demonstrates for the first time that cautious reduction in hydrocortisone equivalent doses leads to increases in BMD, whereas dose increments reduced BMD. These data emphasize the need for the lowest possible GC replacement dose in AI patients to maintain health and avoid long-term adverse effects.