Microadenomas of the human pituitary.

Four hundred and thirty-four pituitary glands from an unselected autopsy series were examined to investigate the incidence and immunohistochemical nature of occult pituitary microadenomas. Fourteen tumors (3.2%) were identified. The ages of the affected patients varied from 11 to 86 yrs, with no age predominance. Males and females were similarly affected. Nine of the microadenomas were available for immunoperoxidase staining. Adrenocorticotropic hormone, follicle stimulating hormone, growth hormone, luteinizing hormone, prolactin and thyroid stimulating hormone were examined. Four of the adenomas were reactive for prolactin; one was reactive for growth hormone, with scattered positivity for adrenocorticotropic hormone, follicle stimulating hormone, luteinizing hormone and thyroid stimulating hormone; 4 were nonreactive.