My son, age 35, has anxiety. Physical: normal bp, but high (100) heart rate. No hyperthyroidism. Other physical causes of both? Beta blocker help?

Anxiety issues. I agree with dr. Werner's list of differential diagnoses of anxiety, which can itself cause many physical symptoms. However, i respectfully disagree that xanax is the best long-term anxiety treatment, and suggest seeing a psychiatrist for evaluation and recommendations. Xanax can help temporarily but is habit-forming. Other, safer options include psychotherapy, buspar, (buspirone) ssri's, inderal, etc.
Complex. Good run down in space allowed! other considerations include infection, heart failure, av fistua, anemia, malnutrition or most any underlying chronic illness. Anxiety is likely but is a DX of exclusion. A lipophilic beta blocker like Propranolol can help. Xanax (alprazolam) is also used rather than valium.