What Causes Enlarged Lobes On Thyroid Gland?

My reports said that i hav enlarged thyroid and both the lobes appear enlarged in size and show homogenous tracer uptake.No cold area seen in either lobe of the glanad FT 4 is 0.94 FT 3 is 3.30 TSH is 6.40 Plz let me know what is it?and wht should i do and wht food i take??