A 17-year-old female presents with palpitations and hyperhidrosis for 6 months, along with recent onset of polydipsia and polyuria. Physical exam shows significant weight loss, mild exophthalmos, grade II thyroid gland enlargement, and vascular bruit audible at both upper poles. Lab results: FT<sub>3</sub> 33.5 pmol/L, FT<sub>4</sub> 40 pmol/L, TSH 0.01 mU/L (0.01 μIU/mL). After controlling hyperthyroidism, what is the likely prognosis for diabetes mellitus (DM)?