Cushing's syndrome, which is characterized by excessive circulating
glucocorticoid concentrations, may be due to
ACTH-dependent or -independent causes that include anterior pituitary and adrenal cortical
tumors, respectively.
ACTH secretion is stimulated by CRH, and we report a mouse model for
Cushing's syndrome due to an
N-ethyl-N-nitrosourea (ENU) induced Crh mutation at -120 bp of the promoter region, which significantly increased
luciferase reporter activity and was thus a gain-of-function mutation. Crh(-120/+) mice, when compared with wild-type littermates, had
obesity, muscle wasting, thin skin,
hair loss, and elevated plasma and urinary concentrations of
corticosterone. In addition, Crh(-120/+) mice had
hyperglycemia, hyperfructosaminemia,
hyperinsulinemia,
hypercholesterolemia,
hypertriglyceridemia, and hyperleptinemia but normal
adiponectin. Crh(-120/+) mice also had
low bone mineral density,
hypercalcemia,
hypercalciuria, and decreased concentrations of plasma PTH and
osteocalcin. Bone histomorphometry revealed Crh(-120/+) mice to have significant reductions in mineralizing surface area,
mineral apposition, bone formation rates, osteoblast number, and the percentage of corticoendosteal bone covered by osteoblasts, which was accompanied by an increase in adipocytes in the bone marrow. Thus, a mouse model for
Cushing's syndrome has been established, and this will help in further elucidating the pathophysiological effects of
glucocorticoid excess and in evaluating treatments for
corticosteroid-induced
osteoporosis.