What Causes Shrinking Of Ovaries?

Mam I am having periods from last two months and am having hot flashes. Actually i was having endometric cyst in my right overy which was removed 5 years back . After 3 years again same problem in lefy overy then i have undergo laproscopy surgery and only cyst was removed. Dr. suggested me to have decapeptyl injections in second and third month of surgery. after this periods become irregular. Now I have ultrasound in which Dr. told me that ur one overy is already not thee and second one is shrinking. please suggest