<s>[INST] My son is 21 yrs old with a near syncope episode and irregular heart rate yesterday. He lost 40 lbs without trying within a couple months. The Dr. said his blood tests xrays and EKG were okay and sent him home. As a baby and until his teenage yrs he suffered from severe asthma and had to receive IM Epinephrine frequently. His maternal grandfather is in remission from Lymphoma. Any suggestions as to cause? [/INST] Hello! Welcome to Ask a Doctor service! I passed carefully through your question and would explain that his excessive loss in the weight is really concerning and should be investigated for a possible metabolic disorder. For this reason, I would recommend consulting with his attending physician for a physical exam and some tests: -a cardiac ultrasound- an ambulatory 24-48 hours ECG monitoring for possible cardiac arrhythmia-thyroid hormone levels for possible thyroid gland dysfunction- cortisol plasma levels for possible a Chat Doctor.  Hope you will find this answer helpful! Wishing all the best,  </s>