By your description of your self it seems you are perfectly normal healthy man with a good life style except for the disc prolaps
Your Hb is well within normal limits, SGPT value is also not high it may be called as insignificant change.
SGPT along with SGOT
enzymes this enzymes increase in the blood when liver gets damaged.
Liver usually gets damaged when taking alcohols or excess drugs.
You havent mentioned whether you are a diabetic or not. You also mentioned you are having disc prolapse
, may be you would have been taking pain killers which causes slight liver injury
But I repeat again your liver SGPT values are very normal. Nothing to worry.