thank you. significant weight loss
with drenching night sweat obviously have some pathology. have you fever,cough,back pain
,bony pain or enlarged nodule at the neck or axilla?
at this old age,there are some possibilities like chronic leukemia
,lymphoma,prostate malignancy or chronic infection(TB).
proper physical examination with some relative inv. as cbc,pbf,psa,x-ray of chest,usg of abdomen is needed to find out the cause.