My PCP gave me RX for a pituitary MRI, since I did not respond to Clomid (my LH did not increase). I suspected that results will come in negative - since my other pituitary hormones are ok, and I do not have classic tumor symptoms (headache and vision problems). I went for MRi today, and got a call - everything seems to be normal of scan. So, if I am secondary, then it is 'idiopatic'. HRT doctor told me same thing - it is likely NOT a tumor, because it turns out to be the problem in minority of cases. Most of the time the reason remains unknown.