[Three cases of Klinefelter syndrome in childhood--endocrinological and gonadal changes in puberty]

Three children at the ages of 4, 10 and 12 years, with external genital malformation, were diagnosed to be with the Klinefelter syndrome by chromosome analysis. To clarify the pubertal changes in this syndrome, all of them were studied for physical and endocrinological examinations and two underwent testicular biopsy. Before puberty any remarkable abnormality were not observed in the hypothalamus-pituitary-gonadal axis and in the physical status. After the onset of puberty they started showing increases of the basal levels of plasma FSH and LH with over-response to LH-RH stimulation test. During the period of this study the levels of plasma testosterone were in the normal range and increased gradually with age. One boy showed a transient high level of plasma testosterone at early puberty. The reactions of plasma testosterone to HCG stimulation of all cases showed the normal pattern. The histological examination of the testis revealed that the number of spermatogonia was reduced in both cases compared with that of normal boys reported by Mancini et al. These findings indicate that most endocrinological and histological abnormalities in adult Klinefelter syndrome occur after the onset of puberty. These changes may be induced at puberty by hypergonadotrophic condition which result from slightly impaired testicular function which is present before puberty.