I'm 32. i recently noticed an obvious change in my leg hair, it became patchy. i haven't noticed that anywhere else. at first it was just front part of thigh, but now inner and lower part. no recent product change. which tests should be done?

If there is no hair loss elsewhere, hormonal issue such as thyroid disease or vitamin deficiency is very less likely present. You are also too young for problem with circulation to the legs. Poor circulation to the legs also causes claudication (calf pain with walking a distance). So the remained possible causes will be local such as fungal infection (hair loss + rashes) or change in gartment.