Suppressed levels of serum cortisol following high-dose oral dexamethasoneadministration differ between healthy postmenopausal females and patients with established primary vertebral osteoporosis

Hypercortisolism and glucocorticoid treatment, even in a low dose or admini stered topically, may influence bone metabolism. It was the aim of this stu dy to investigate whether there might be differences in the regulation of e ndogenous cortisol secretion between patients with established primary vert ebral osteoporosis and healthy controls. Suppressed morning serum cortisol concentrations in a 3 mg dexamethasone overnight suppression test were comp ared in well-defined healthy postmenopausal women (n = 149) and osteoporoti c patients classified as having established primary vertebral osteoporosis with no clinical features of hypercortisolism (n = 78). Suppressed cortisol in the healthy controls was 1.08 +/- 0.44 mug/dl and in the primary osteop orotics 1.58 +/- 1.42 mug/dl (p < 0.0001). Of the investigated primary oste oporotics 15.4 % (n = 12) had suppressed cortisol levels above the 97.5th p ercentile (1.96 <mu>g/dl) of the healthy controls. Subgroup analysis regard ing the influence of gonadal steroid hormone replacement in both groups and gender in the osteoporotic group did not change the results. Four of the 1 2 patients with incomplete suppressive cortisol underwent adrenal endosonog raphy, unilateral adrenal nodular hyperplasia being detected in three cases . In two patients the diagnosis was confirmed by histology and normalisatio n of a dexamethasone suppression test following endoscopic adrenalectomy. T hese data yield evidence for a difference in the regulation of cortisol sec retion following high-dose dexamethasone administration between healthy sub jects and a subgroup of patients with primary osteoporosis. This might be d ue to a relevant amount of autonomous cortisol secretion in some of these p atients; however, even cortisol resistance has to be taken into account.