LACK OF PINEAL GROWTH DURING CHILDHOOD

During childhood, serum melatonin concentrations drop by approximately 80%, but the 24-h melatonin excretion is stable. Arrest of pineal gro wth after the end of infancy has been proposed as one possible mechani sm underlying that phenomenon. To test this hypothesis, we reviewed 33 2 magnetic resonance imaging brain studies, classified as normal, of e ndocrine-normal children, aged 1 day to 15 yr, and estimated the pinea l and pituitary sizes. The pineal was identified in 277 of 332 magneti c resonance imaging studies (83%). The average size (mean If: SEM) of the pineal gland (transaxial diameter, 5.6 +/- 2.1; midsagittal diamet er, 5.0 +/- 2.4; planimetric area, 28.5 +/- 17.8) did not differ with age. A total of 74 of 277 pineals with cysts (26.7%) were found. The o ccurrence of pineal cysts was equally distributed among the different age groups (chi(2) = 11.6; df = 14; P = 0.7). Ten pineals showed more than 1 cyst (3.6%). The pituitary was identified in 325 of 332 brain i mages (97.9%). The average pituitary size increased by some 100% from 1 to 15 yr of age [transaxial diameter: F = 2.2; P = 0.005 (by two-way analysis of variance); midsagittal diameter: F = 3.7; P = 0.0001; pla nimetric area: F = 7.1; P = 0.0001]. The pituitary was slightly larger in females than in males [midsagittal diameter: F = 8.8; P = 0.003 (b y two-way analysis of variance); planimetric area: F = 7.9, P = 0.005] . The data presented indicate a lack of a discernible pineal growth af ter age 1 yr, which contrasts with pituitary development in the same i ndividuals. The data are in agreement with a hypothesis suggesting a g rowth arrest of the pineal after infancy.