Hypothyroidism cannot be controlled by exercise. You can help it by avoiding cabbage family of vegetables and having iodinated salt. However the cause needs to be seen, whether you have autoimmune hypothyroidism, which will require medicine. Also, a TSH of 5.8 may or may not require treatment unless you have clear symptoms of thyroid disease. In case you do actually need treatment, do not fear it as it's quite harmless but has a lot of benefits.