Aims: Bone mineral density (BMD) may be potentially reduced in Addison's disease as a result of excessive glucocorticoid replacement, loss of adrenal androgens or concomitant gonadal or thyroid disease. We have examined clinical and biochemical parameters, and BMD in a group of subjects with Addison's disease.
Methods: Fourteen patients (9 female mean age 56 years, 5 male mean age 56.6 years) with primary adrenocortical failure (median duration 8.5 yrs) on replacement therapy were studied. Four had hypothyroidism on thyroxine doses (0.1 to 0.15 mg/d). Seven of the 9 females were post menopausal. Mean plasma cortisol levels were calculated from at least five samples in each subject drawn between 3 and 5 hours post dose, and the cortisol replacement dose calculated per unit body mass (mg/kg). BMD was measured by dual energy X-ray absorptiometry (DEXA) at femoral neck and lumbar spine (L2-4) and compared with local reference data.
Results: For women (n = 9) at L2-4 the mean Z score was -1.21 (95% CI -1.69, -0.73), and at femoral neck -0.57 (95% CI -1.15, 0.00). For men (n = 5) at L2-4, the mean Z score was 1.32 (95% CI -0.86, 3.50) and at femoral neck 0.62 (95% CI -0.18, 1.42). For all patients, there was no significant correlation between mean plasma cortisol and Z scores at L2-4 and femoral neck, r = -0.003 and -0.095 respectively; and between duration of Addison's disease and mean Z scores at L2-4 and femoral neck r = -0.043 and 0.143 respectively.
Conclusions: Women with Addison's disease therefore have a greater than expected reduction in BMD. We postulate that this may be related to loss of adrenal androgens.