A. Accumulation of uric acid leads to gout. It is a form of arthritis in which there is severe pain, redness and tenderness in joints.
B. Immune disorder affecting neuromuscular junction leads to myasthenia gravis. It is a neuromuscular disorder that causes weakness in the skeletal muscles which are under control.
C. High concentration of calcium and sodium which leads to hypercalcemia and hypernatremia.
D. Decreased level of estrogen leads to osteoporosis. In this bones become weak and brittle.
So, the correct answer is 'Decreased level of estrogen'.