Endocrine Pathology in Paediatrics

Abstract

The cortical tissue of the adrenals arises in the posterior coelomic mesoderm close to the genital ridge and can be identified at the 10-mm stage (6th week). At birth their combined weights average 6.5 g, with the bulk of this relatively large mass comprising a specific fetal cortical zone. This is composed of masses of large eosinophil cells that show ultrastructural characteristics similar to those of the adult adrenal cortex. The definitive cortex forms a sharply contrasting narrow zone of small cortical-type cells beneath the gland capsule. Degenerative involution of the fetal cortex starts at or shortly before birth and is virtually complete within the first few months of postnatal life, though remnants may occasionally be found up to the end of the first year. The definitive cortex shows conspicuous evidence of growth by the 4th day after birth and the zona glomerulosa and zona faciculata are defined by the 6th week. As a result of involution of the fetal zone the combined weights decrease from birth to an average of 3.5 g at 3 months, after which they increase steadily in size in relation to body weight to reach 6 g at about 12 years of age. The normal development of both the fetal and the definitive cortex is to a large extent dependent on normal hypothalmic and pituitary function since the fetal zone is found to be markedly reduced and the definitive cortex less conspicuously so in cases of anencephaly (Fig. 13.1). Similar failure of development of the rat adrenal can be induced experimentally by destruction of the hypothalamus. The fetal zone is observed to be of increased size in babies born to mothers with diabetes mellitus and in cases of postmaturity.