Pituitary cells can increase and shrink in number at any moment in life depending on stimulation from hypothalamic release factors, or lack thereof.
In the case of LH it's reasonable to envisage a reduction in number of gonadotrope (both FSH and LH producing) cells, but this is ultimately the result of cessation of GnRH input from the hypothalamus via the pituitary stalk... if that were to resume then any change to above cells would likely be reversed.