, Volume 139, Issue 1, pp 8-12

Puberty in 24 patients with Klinefelter syndrome

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Twenty four boys with Klinefelter syndrome, 18 of whom were diagnosed prepubertally, were observed until adulthood. Onset of puberty, as judged from testicular enlargement and pubic hair development, occurred between 11 to 14 years in the above 18 patients. By the age of 17 pubic hair, penile length and height had reached the adult stage in all patients, but arrest of testicular growth was noted at midpuberty, 13 years, with maximal mean (±SD) volume attained being 3.5±1.5 ml. The first conscious ejaculation was reported to have occurred between 13 to 16 years in 10 patients and in the remaining 4 between 17 to 18 years of age. Sperm counts obtained after the age of 18 revealed azospermia or severe oligospermia in all patients except one, who had a sperm count of 30×106/ml. The hypothalamic-pituitary-gonadal axis, assessed by LH-RH and hCG stimulation tests, was found to be normal in prepuberty and during early pubertal stages. From mid-puberty the basal levels of plasma FSH and the response to LH-RH showed a gradual increase above the normal. Towards late puberty (>15 years) basal and peak levels of LH were above normal with a concomitant decrease in the basal level of testosterone and its response to hCG.

These findings indicate that during childhood and early puberty function of the hypothalamic-pituitary-gonadal axis is normal in Klinefelter syndrome, allowing the onset of pubertal signs at the appropriate age, and that until late puberty there is a relative preservation of function in the testicular Leydig cells, permitting the normal sequential development of the androgen-dependent pubertal signs. The measurement of testicular testosterone reserve by means of hCG stimulation constitutes a useful aid in determining when and if testosterone replacement therapy should be instituted.