Assertion- An example of age-related disorder characterised by decreased bone mass is osteoporosis
Reason- It is caused due to defect in purine metabolism

The correct option is C The assertion is true but the reason is false
Osteoporosis- It is an age-related disorder characterised by decreased bone mass and increased chances of fractures. Decreased levels of estrogen is a common cause. Osteoporosis is a bone disease that occurs when the body loses too much bone, makes too little bone, or both. As a result, bones become weak and may break from a fall or, in serious cases, from sneezing or minor bumps. In this disease, bone becomes porous.
Usually, defects in purine metabolism lead to accumulation of uric acid in the joints that lead to gouty arthritis.