Gout happens due to the accumulation of $...$ in joints.

Osteoporosis,an age-related disease of the skeletal system,may occur due to:

Decreased level of oestrogen in the human body leads to:

In Myasthenia gravis . . . . . . is affected.

Select the correct statement regarding disorders of the muscular or skeletal system.

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$:
Osteoporosis is characterised by decreased bone mass and increased chances of fractures.
Reason $(R)$:
Common cause of osteoporosis is increased levels of estrogen.
In the light of the above statements,choose the most appropriate answer from the options given below: