Hypopituitarism following pituitary irradiation for acromegaly.

Endocrine evaluation is reported in 8 acromegalic patients who received 5,500 rad to the pituitary from a linear accelerator. There was a mean decrease in hGH levels of 72%. Plasma testosterone levels were low in 1 of the 6 male patients prior to pituitary irradiation and were below normal in all male patients on the final evaluation (3.1 +/- 0.2 SD years postirradiation). Deficiency of TSH secretion developed in 2 patients following irradiation. This rather high incidence of postirradiation partial hypopituitarism was not anticipated, and is thought to be related to radiation necrosis of the normal pituitary tissue which surrounds the adenoma.