8mth old 151/2lbs 2 1/2ft head cirm 56 should these measurements be cause for concern?he eats very well. should we see endocrinology for testing?

You need accurate : Measurements at your pediatrician's office ; velocity of head ; body growth since birth. A 56 cm. Head circumference is so far >97th%ile that his doctor would order a stat MRI of the brain. To plot points on growth curves accurately, use age in months ; days. If true recumbent length is > 97th%ile ; true weight is < 5th%ile, his pediatrician will look for causes of tall stature ; undernutrition.