True about osteoporosis -
Osteoporosis is a metabolic disease.Its characterised by diffuse reduction in bone density.due to decrease in bone mass.It occurs when rate of bone resorption exceeds bone formation. C/f: Loss of bone mass leads to loss of strength so that trivial trauma is sufficient to cause a fracture. A slight loss of height and increased kyphoisis duevto compression of anterior part of vertebral bodies. Radiological findings- Loss of vertical height of a vertebra due to collapse. 
Cod fish appearence- The disc bulges into the adjacent vertebral bodies so that the disc becomes biconvex. Ground glass appearence Serum calcium ,phosphorous and alkaline phosphatases are within normal limits.
Total plasma proteins and albumins may be low.
Low calcium
Low phosphate
Cod fish vertebrae
Raised alkaline phosphatase