PITUITARY SIZE ASSESSED WITH MAGNETIC-RESONANCE-IMAGING AS A MEASURE OF GROWTH-HORMONE SECRETION IN LONG-TERM SURVIVORS OF CHILDHOOD-CANCER

We investigated 37 long term survivors of childhood cancer to study th e relationship among growth, GH secretion, and pituitary size. The med ian follow-up time after diagnosis was 13.2 yr. The pituitary gland wa s visualized with magnetic resonance imaging. Radiated patients (n = 2 5) had a reduced relative height and showed a greater reduction in rel ative height after diagnosis than nonradiated patients (n = 12). The p atients had lower spontaneous nocturnal GH secretion than controls due to a reduced peak amplitude. Spontaneous GH secretion was lower in ra diated patients than in nonradiated subjects. The patients had lower p lasma insulin-like growth factor-I (IGF-I) and serum IGF-binding prote in-3 (IGFBP-3) concentrations than the controls. Radiated subjects had decreased IGF-I and IGFBP-3 concentrations compared to nonradiated su bjects. Half of the patients (20 of 37) evaluated with magnetic resona nce imaging had a reduced pituitary size (pituitary height, <-2 so sco re). Radiated subjects had smaller pituitary glands than nonradiated o nes. Seventeen of 20 patients (85%) with reduced pituitary size had de creased nocturnal GH release. There was a positive correlation between nocturnal GH secretion, plasma IGF-I, and serum IGFBP-3 levels, on th e one hand, and pituitary height, on the other. These results indicate that cranial radiation may result in tissue damage, leading to decrea sed pituitary size, reduced spontaneous GH secretion, and impaired lin ear growth, The finding of reduced IGF-I levels in both radiated and n onradiated patients combined with decreased IGFBP-3 concentrations in radiated patients, indicates that cytotoxic chemotherapy may induce he patic damage resulting in decreased IGF-I synthesis.