What Causes Diminishing Of Strength And Dexterity In Hands?

Hi, I ve lost all the muscle between my thumb and first finger on both hands and the strength and dexterity in both hands has diminished considerably but they have never hurt and I just thought it was a natural occurrence of aging, I m 72. Recently, I ve been told it s not natural and I probably have some sort of problem so I m wondering if I have. I must admit I do not like how weak and infirm my hands have become and I must ask others to button shirts or open packages or any exercise that requires dexterity or strength. What do I have. Thank you, Denny