How to know if testicles have reduced ? by blood analysis of lh and fsh only ?

Don't understand: By testicles do you mean testosterone secretion? Testes generally don't decrease without a significant medical problem or intervention, such a receiving testosterone, which you are getting for ? Reasons. It would be unlikely to have low testosterone at your age. Are you taking t for muscle building? If so, it's going to have side effects you don't want. Lh/fsh won't help if taking t injections.