If i had a thyroid scan that read: left lobe of gland is mildly enlarged at 5.8cm x 1.7 x 2.2 . there is a avascular 3 mm hypoechoic nodule in the lower pole of the left lobe. how would i know if it was " hot or cold"?

Different tests: You had a thyroid ultrasound which evaluates the anatomy of your thyroid gland. To find out if a thyroid nodule is hot or cold you need a nuclear thyroid scan aka i-123 uptake and scan. This latter is a functional test of your thyroid and characterizes nodules as hot, cold or warm (isointense). However, a 3 mm nodule is likely to small to characterize with a nuclear thyroid scan.

Can't tell: The test you stated above is a thyroid ultrasound. It is not a scan. You can't tell if something is hot or cold definitively on a thyroid ultrasound. You need a thyroid scan (using radioactive iodine) to know if something is hot or cold. If your TSH was normal, you probably didn't have a scan for a nodule that small (3 mm).

No way: The thyroid scan with i123 radiopharmaceutical is accumulated by the thyroid gland. Scan shows no activity in area of avascular or cold nodule. Ultrasound of thyroid can determine if the nodule is probably cyst or neoplasm. 3mm is quite small. Follow up esamination with us in a few months to see if stable or growing. Might have biopsy of the lesion if suspicious for something other than cyst.

Ultrasound results: What you are describing are ultrasound results. A hypoechoic nodule of 3 mm of size is nearly 100% benign. The only reason to assess if a nodule is overactive (hot) or underactive (cold) is in general hyperthyroidism. If the nodule is hot, then it can be the target of therapy. This is done through a i-131 uptake and scan.