Hormone study in a case of Klinefelter syndrome with an isochromosome Xq

We investigated the endocrine function of a patient with Klinefelter syndrome in which the extra chromosome was an isochromosome Xq. This man was azoospermic but with normal secondary sex characteristics; smallness of the testes was the only abnormal physical finding. High follicle-stimulating hormone (FSH, 70 mIU/mL) and moderately elevated luteinizing hormone (LH, 40 mIU/mL) were found; the FSH and LH response to LH-RH was exaggerated. Androgen and estrogen levels were normal. The insulin test (measure of glycemia, growth hormone, and corticol) and the test with TRH (measure of TSH and prolactin) gave normal results. We conclude that the presence of additional long arms of the X chromosome is sufficient to cause Klinefelter syndrome and that the presence of two extra Xq does not intensify the degree of androgenic insufficiency.