Does any of you have a case of congenital absence of a pituitary gland?

Very rare. Only a small handful of this lethal congenital malformation have been described. It is usually associated with adrenal hypoplasia. It should not be confused with the empty sella syndrome which gives the appearance of an absent pituitary on ct or MRI scan.
Absence of Pituatary. There ae many published cases of congenital absence of the pituatary gland. A place to start looking is the journal of pathology and bacteriology, volume 73, issue 1, pages 59-67, january 1957. You will find other sites on the internet.