Hello,
Thank you for your query at DoctorSpring.com
Presence of TPO antibodies alone doesn't mean anything unless TSH is high. Antibodies may be present in normal individuals too. Your degree of TSH increase doesnot increase weight as you think it does and treating it with thyroxine supplementation will not help much either. Weight gain is because of mismatch between dietary intake and exercise/energy expenditure and you need to tackle it with diet restriction and increasing your exercise.
No further testing is necessary here.
Feel free to discuss further,
Regards.