What is the best description of Addison's disease?
A. It is caused by the overproduction of growth hormone by the pituitary gland.
B. It is caused by a lack of insulin production by the pancreas.
C. It is caused by the overproduction of parathyroid hormone by the parathyroid gland.
D. It is caused by the lack of cortisol and aldosterone production by the adrenal gland.