Had hemithyroidectomy last year, the bit of thyroid that's left has a lump 2.5 x 3 cm. the scan showed it has electrolytes in it, what does this mean?

Electrolytes?: Electrolytes mean calcium, sodium, potassium, magnesium etc....Thyroid scan cannot see these electrolytes. 2.5x3cm is a relatively large thyroid mass and, especially if it is solid, biopsy is likely needed. Why did you get the hemithyroidectomy in the first place? Concern of cancer? It is possible that you will need total thyroidectomy. I recommend follow-up with doc. Good luck.