Hormone in balance. Give solution!

Sir my son age 12 years, his pennise size is 6cm now,   we are consultant endocrine from 2016, on that time do some tests testosterone, lh fsh ,prolactin,digital x Ray for brain , ultrasound testies, on that time lh hormone levels low, other tests normal,on that time pennise size 4.5cm, doctor say comes after one year , consulting one year he do testosterone levels 2.5ng/Dl pennise size 4.5cm he gives,testosterone injection monthly 50 mg gives 3 months and stop after 4 month his pennise 5.5 cm he comes after 6 months, pennise size same then gives same dose testosterone pennise size 6cm,and stop present age 12 years, hair growth start at internel parts sir please give right direction this is problem ,or age unda, we are show any other doctor please give solution