Could male taking clomiphene for years have attenuation of endogenous LH production from pituitary?

Probably not. Clomiphene works by blocking estrogen at the pituitary. The pituitary sees less estrogen, and makes more lh. More LH means that the leydig cells in the testis make more testosterone. I don't see how Clomid (clomiphene) would cause the LH production to attenuate.