(Reuters) - Insurer American International Group Inc missed analysts' estimates for third-quarter profit on Friday due to weakness in its life and retirement business.Pre-tax income from the business fell 9% to $646 million (£499 million) as it booked a $143 million charge related to a review of its actuarial assumption.The company is among a number of life insurers that typically conduct reviews every third quarter of assumptions they made when writing policies many years ago. Excluding the..